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MEMORY FAQ (please read before posting)

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September 27, 2005 6:34:31 PM

wOOtz!

Great job!! Now if we could just get Fredi to make it a sticky...

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September 27, 2005 8:39:30 PM

A GUIDE TO UNDERSTANDING MEMORY

INDEX

1. KEY TERMS
2. MEMORY MODULE FORM FACTORS
3. MEMORY MODULE TECHNOLOGY
4. RAM TECHNOLOGY
5. MEMORY MODULE IDENTIFICATION
6. MEMORY CHIP IDENTIFICATION
7. MEMORY MODULE CLASSES
8. MEMORY CHIP CLASSES
9. TABLE OF STANDARD SPECIFICATIONS (WITH LATENCY)
10. BEFORE YOU PURCHASE
11. INSTALLING MEMORY
12. TROUBLESHOOTING
13. GENERAL QUESTIONS
14. VIRTUAL MEMORY
15. MANUFACTURERS
16. BROKERS
17. COUNTERFEIT MEMORY
18. RAM GUIDES


__________________________________________________
1. KEY TERMS
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CL: Short for CAS Latency, where CAS is short for Column Address Strobe. CL latency is one of the most important parameters of a memory chip. It is the time it takes to get data to the data pins. Immediately following the CAS Latency, the data is available on the memory Data-pins.
Command Rate (CMD): The command rate specifies how many consecutive clock cycles need to be sent to the memory modules before the modules can send data. Because wires often have natural capacitance on them, sometimes it takes longer for a wire to transition from a 1 to a 0. The CMD setting is typically one or two clocks and can often be adjusted between the two. It's represented as 1T or 2T.
CPU: Stands for Central Processing unit. Also called processor, the CPU is the active part of a computer where arithmetic operations are performed.
Core speed/frequency: The speed of the innermost component of an electronic device, measured in MHz.
Example: A DDR-400 module has core speed of 200MHz.
DRAM: Dynamic Random Access Memory
Dual-channel: A property of the motherboard where the memory bus is split into two 64-bit channels, effectively doubling the bandwidth in relation to a single-channel setup. Dual-channel is not a property of the memory modules.
Effective speed/frequency: The actual speed of a device in practice, measured in MHz.
Example: A DDR-400 module has an effective speed of 400MHz.
Form factor: The physical size and shape of a device.
FBGA or BGA: Fine Ball Grid Array
FSB: Stands for front side bus. The FSB is the data path that runs between the CPU and main memory (RAM).
IC: Integrated Circuit, commonly referred to as a memory chip, an IC is a small electronic device made out of semiconductor material.
Latency: Physical delay of the memory module represented discreetly in clock cycles. Usually pronounced as 'C-L three', where the three represents the delay, measured in clock cycles. The delay normally ranges from two to six clock cycles for DDR.
Memory module bank: Logical division of chips on a PCB board. A single memory bank can be composed of any number of chips. Some banks are composed of only 2 chips, whereas some other modules have 18 chips or more per bank. Not to be confused with memory Rank, see next term.
Memory rank: The physical side of a memory module. The side of the module is referred to by Rank0 or Rank1.
PCB: Stands for printed circuit board. A PCB is a small plate on which chips and other electronic components such as resistors or capacitors are placed.
Semiconductor: A material such as germanium or silicone which allows current to flow under certain circumstances. Semiconductor materials make it possible to make energy-efficient and fast nano-scaled transistors, which are the basic units of computer logic. Semiconductor materials are used in the fabrication of integrated circuits, which are used to build memory modules.
TSOP: Thin Small Outline Package


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2. MEMORY MODULE FORM FACTORS
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SIMM: Single in-line memory module. An older technology, a SIMM is a PCB (Printed Circuit Board) that typically holds 8 or 9 memory chips on a single 32-bit data bus. Typically comes with 72-pins.
DIMM: Dual in-line memory module. A DIMM is a PCB (Printed Circuit Board) that can hold up to 18 chips on a single 64-bit data bus. DIMMs make up a range of different pin configurations: 168-pins for SDRAM, 184-pins for DDR, and 240-pins for DDR2.
RIMM: A Rambus trademark name for a module that uses RDRAM chips, similar to a DIMM, but with different pin configurations. The number of pins: 184-pins for 16-bit modules, 232-pins for 32-bit modules. RDRAM modules have heat-spreaders on them and use RAMBUS technology
SO-DIMM: Small outline DIMM. An SO DIMM is about half the length of a DIMM and is typically used in notebook systems. An SO-DIMM has the following pin configurations: 144-pins for SDRAM, and 200-pins for DDR and DDR2.
SO-RIMM: A small outline RDRAM module for notebook systems, similar to an SO-DIMM, but uses RAMBUS technology.
MICRO-DIMM: Basically a small form factor SO-DIMM. Micro-DIMMs are used primarily in small notebooks and mini PCs.


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3. MEMORY MODULE TECHNOLOGY
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UNBUFFERED MODULE: A buffer is used to re-drive and refresh a signal as it travels on a wire. An unbuffered memory module has no such buffer. Unbuffered memory modules are the most common for desktop systems.
FULLY-BUFFERED MODULE: A module whose data signals are re-driven and refreshed before sent. These modules are typically used for server applications where many high-speed DRAM components are required. FBDIMM modules are a new technology complementing current registered memory technology.
ECC MODULE: Stands for error-correcting code. An ECC module has an additional memory chip per memory bank that is responsible for detecting and correcting 1-bit data errors as data passes through the memory module.
REGISTERED MODULE: A registered module contains an extra memory chip per memory bank that is responsible for holding data for one clock cycle. This process increases the reliability of data. Typically, registered modules are only used in data-sensitive or server stations where the focus is on the integrity of data. Registered modules are not compatible with desktop motherboards.


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4. RAM TECHNOLOGY
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FPM: Fast page mode RAM. Popular at one time, FPM RAM allowed for faster access to memory, but was replaced by newer technology such as SDRAM.
EDO: Extended data out DRAM. Essentially modified FPM technology, EDO RAM allows the possibility of fetching the next block of data at the same time it sending the previous block.
DRAM: Dynamic random access memory.
SDRAM: Synchronous DRAM. The clock speed of an SDRAM module is synchronous with the CPU bus.
RAMBUS: A bandwidth driven bus technology where high speed data transfers are possible through a feature where operations occur on both the rising and falling edge of the clock signal. Rambus technology uses a packet-switched bus where addresses/data are multiplexed, instead of using row and column address strobes like in SDRAM and DDR systems.
DDR SDRAM: Double data rate SDRAM. The core-clock speed of a DDR SDRAM module is synchronous with the CPU bus, however data is sent on both the rising and falling edge of the clock signal effectively doubling the memory chip's throughput.
DDR2 SDRAM: Next generation DDR technology, DDR2 memory offers greater bandwidth and density in a smaller chip-package. DDR2 requires less power than its DDR predecessor, and is composed of a technology that allows for greater speeds of 400, 533, 667, 800 MHz, and above.


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5. MEMORY MODULE IDENTIFICATION
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Q: For the modules installed in my system, how do I find the following?

TYPE OF RAM
A: You can find the type of RAM in the memory section of CPU-Z (from www.cpuid.com). Also, you can check the motherboard's manual to see what type of RAM it supports.

SIZE OF MEMORY INSTALLED
A: You can find the size of memory installed using CPU-Z.

SIZE OF MEMORY RECOGNIZED BY WINDOWS
A: double-click the 'system' icon in the control panel.
Start --> Settings --> Control Panel --> Syetem. Look under the general tab, you should see something similar to "512 MB of RAM"

You can also use CPU-Z.

BRAND OF MEMORY
A: You can normally find the brand by looking directly at the modules themselves. If no sticker, label or logo exists on the module, sometimes you can find the brand labeled on the chips.

CHIP CONFIGURATION OF THE MODULES
A: Please refer to section: MEMORY CHIP IDENTIFICATION.

SPEED OF MY RAM
A: Under the memory section of CPU-Z you will find a text box labeled as 'Frequency'. This is the core speed of the module. Keep in mind for DDR the effective speed is double the core speed.


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6. MEMORY CHIP IDENTIFICATION
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A good way to identify a module is by looking at its chips. Sometimes it's difficult to identify the chips, either because the chips are non-major brand, or covered by a heat spreader.

To identify the part numbers on major brand chips or modules, please refer to the following documentation (you can also check the chip part numbers on the modules with the manufacturer's web):
http://www.samsung.com/Products/Semiconductor/DRAM/index.htm SAMSUNG
http://www.micron.com/products/search.aspx MICRON
http://www.infineon.com/cgi-bin/ifx/portal/ep/channelView.do?channelId=-54803&channelPage=%2Fep%2Fchannel%2FproductCategories.jsp&pageTypeId=17099&BV_SessionID=@@@@1772206913.1127858201@@@@&BV_EngineID=ccckaddfklghigjcflgcegndfifdfoi.0 INFINEON
http://www.hynix.com/eng/02_products/01_dram/dram_01.jsp HYNIX
http://www.elpida.com/en/products/index.html ELPIDA

For other modules, you can check the manufacturer's web site for further details if the module is not listed here:
http://www.ocforums.com/showthread.php?t=308361 OC FORUMS


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7. MEMORY MODULE CLASSES
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Picking the right memory is typically a preference; there is no single memory module that is better than the others.

Memory can be classified into the following general classes:

Memory Classes: (note: sort these by classes/tiers)
1. Performance modules
2. OEM or third party
3. Major original
4. Major third party
5. Second-tier
6. Downgrades
7. Counterfeit


Performance Modules
Typically any module rated to perform above the market standard.
Examples: DDR500+ or PC-3200 CL2 modules.

Third party modules
Any module manufactured by one company using chips built by another company. For example, a module built by Kingston using Samsung chips is a third party module.

OEM
OEM (original equipment manufacturer) is a confusing and misleading term. OEM is normally described by: A company uses original equipment, such as memory chips, to manufacture the modules. The original equipment (memory chips in this example) is typically branded with the company's name who manufactures the module from the chips; however, the equipment is not usually built by the company, but used by the company. This term is not normally used to describe major or high quality modules, because many OEM modules are built using lower quality parts.

Major original
Any major brand module where the chips and the modules are built by the same company. The standards of testing and manufacturing are normally higher for the major brands.
Major brands:
Class1: Samsung, Micron, Infineon, Hynix
Class2: Elpida, Mosel, Toshiba, Nanya

Major third party
Modules manufactured by one company using major branded chips built by another company.

Second tier originals
Original modules built by major manufacturers, but because the testing standards are usually lowered, the cost of the modules becomes more competitive in the market. Popular Examples: Spektec (Micron), Elixir (Nanya), Aeneon (Infineon).

Downgrades
Modules built using downgraded chips, often called half-bit modules. Sometimes, the chips fall short of their intended standard and have to be passed down to a new standard. Many of the chips are intended as 32M chips for example, but fall short of the memory density and thus are passed off at 16M chips instead.

Counterfeit
The typical counterfeit case involves blank or UTT chips being marked and illegally passed off as major brand chips. They are sold at a higher price, and because the quality is not as good as major brand modules, the reputation of the major brand companies, who provide good quality modules, suffers. Counterfeit chips make up approximately 10% of the market total.


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8. MEMORY CHIP CLASSES
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There are only a handful of chip manufacturers. The value of the chip is determined by the testing process and the availability of the chip in the market. It is fair to say that a large manufacturer whose chips are widely available will be higher in cost than a similar manufacturer whose chips are rarely seen. This is because the reputation and value of a manufacturer is built over time.

MAJOR BRAND IC (tier-one):
The current leader in chip production is Samsung, followed closely by Micron, Hynix and Infineon. These companies have a reputation of maintaining high standards for their ICs. And because the chips are consistently available in the market sets them apart from other major brands.

MAJOR BRAND IC (second-tier):
Other major brands include: Elpida, Mosel Vitelic, Nanya, Powerchip, and Winbond. Not to say the quality is any different than tier-one major brand, the main factor setting them apart is their rank in terms of market share, and availability of chips in the market.

UTT (UnTesTed) CHIPS:
Contrary to its name, UTT chips are tested, but not as thoroughly as major chips. As a result, some have adopted to call them ETT (Effectively TesTed) Chips. Because testing standards have been lowered, the cost of UTT is better than other major brands. Some companies have elected to perform additional testing on UTT chips thereby raising its cost. As a result, performance, quality and cost are random from company to company. Often, UTT chips are remarked and passed on as new specification.


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9. TABLE OF STANDARD SPECIFICATIONS (WITH LATENCY)
__________________________________________________


Memory standards have been in place to provide a medium for the general computer system. Of course, many applications and systems can go safely beyond the standards, but knowing how far a module can go requires some expertise. Thus, the standards have been decided by JEDEC and followed by most manufacturers as a general measure of safe operation for the common computer system. However, many advertised and retail modules deviate from these standards to make the modules more attractive to enthusiasts and general consumers.

Below you will find the official memory standards currently set by JEDEC:

DDR2
DDR2-400 = PC2-3200 (200MHz @ CL=3, tRCD=3, tRP=3)
DDR2-533 = PC2-4200 (266MHz @ CL=4, tRCD=4, tRP=4)
DDR2-667 = PC2-5300 (333MHz @ CL=5, tRCD=5, tRP=5 OR 4-4-4)
DDR2-800 = PC2-6400 (400MHz @ CL=6, tRCD=6, tRP=6, OR 5-5-5)

DDR
*DDR-500 = PC-4000 (250MHz)
DDR-400 = PC-3200 (200MHz @ CL=3, tRCD=3, tRP=3, or 3-4-4)
DDR-333 = PC-2700 (166MHz @ CL=2.5, tRCD=3, tRP=3)
DDR-266 = PC-2100 (133MHz @ CL=2.5, tRCD=3, tRP=3 OR 2-3-3, 2.5-3-3)

SDRAM
PC-100 (100MHz @ CL=2, tRCD=2, tRP=2)
PC-133 (133MHz @ CL=3, tRCD=3, tRP=3 OR 2-2-2)

RAMBUS
PC-800 (400MHz)
PC-1066 (533MHz)

*Non Standard Specification (not officially supported)


__________________________________________________
10. BEFORE YOU PURCHASE
__________________________________________________


DO A LITTLE RESEARCH:
How much memory do I need?
It depends on your type of work. 512MB is enough for most desktop applications such as windows office tools. Some workstations can benefit from upwards of 1GB to 2GB of memory and server stations can use as much as 16GB or more. 1GB seems to be the "sweet spot" for the majority of Windows XP users.

How much memory will my system recognize?
Every system has its own limit on the memory size which varies with each Operating System and motherboard. Check with your motherboard manual on how much memory your motherboard supports. Desktop motherboard limits are typically 3GB or 4GB.

What kind of memory is compatible with my system?
Check with the motherboard manual.

How many sockets are open and how should I fill them?
Motherboards typically have 2, 3, or 4 slots for memory. You'll need to check with the motherboard manual to see if there are limitations on the memory setup.

How do I determine the quality of memory?
The quality of memory lies with the integrity of the module's manufacturer and the type of chips used.

What should I know about memory prices?
Prices vary from company to company- even for the same product. Shopping around is always a good idea. In many cases modules that perform only slightly better may be significantly higher in price. Thus, choosing the right module is often a balance between how much performance you want versus the price of the module.

What kind of service and support do I need?
Some modules come with limited, lifetime or no warranty at all. It is a good idea to buy from a reputable source because almost always the modules will come with a return policy. Of course you want to cross the return policy from several sources before making a decision.

What other issues should I consider?
It is also a good idea to be familiar with different brands, and pay attention to the speed and latency of the module. Some modules are better than others. Matching performance, stability and cost is not always an easy thing to do. If you have other questions regarding your purchase you can always post on the message forums, check with the vendor's website, or consult a professional.


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11. INSTALLING MEMORY
__________________________________________________


1. Make sure you have the correct type of memory module for your system.
2. Make sure the module does not exceed the maximum capacity supported by your motherboard. You can check with the motherboard's manual what capacity is supported.
3. Make sure the module is firmly seated in the slot with the clips locked in. Clean away any dust to ensure good contact between the module and the slot.
4. Make sure the processor and graphics card are firmly seated. They may have been accidentally dislodged by you while installing the module.
5. Check that each module installed on the motherboard is not defective and are not in conflict with one another. Test by first removing all modules from the motherboard. Install each module by itself on the motherboard and try to boot the system. If everything appears to work properly, then install one module, then add back the remaining modules one at a time, booting up the system between each addition, to find any possible sources of conflict.

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12. TROUBLESHOOTING
__________________________________________________


Q: My system does not recognize the full capacity of the modules I installed. How do I fix this?
A:
1. If the system memory appears to be off by several megabytes, then check to see if you have an on-board graphics processor on your motherboard. Often, on motherboards with integrated VGA, a portion of the system memory, such as 8MB, is placed aside for video memory.
2. If the system is recognizing only a fraction, such as 1/2 or 1/4, of the total capacity of the module, then the problem is most likely due to you using modules with memory chips that are too high in density. Many older systems require lower density memory parts. As memory modules with higher megabytes are developed, the density of the memory chips also must increase. Older, lower density memory parts are phased out and become harder to find. Current modules with high density memory components may not work with the older systems.

Q: I added more memory to my system, but I still get warnings that my system resources are low. How can I fix this?
A: System resources and system memory are not the same thing. System memory refers to the physical memory installed on the system- if you have a 128MB module installed on your motherboard, then you should have 128MB of system memory. System resources are areas of memory used to keep track of the windows that are open and displaying objects on the screen. If this area becomes full, programs may not load properly and Windows may become unstable, no matter how much free system memory you have. Closing some running applications can free up your system resources, but some software may not release its resources as readily and you may need to reboot Windows.

Q: I added more memory in my system, but now I get "Out of Memory" error messages in Windows. How can I fix this?
A: If your system memory is 512MB or above and are running Windows 95/98/Me, please consult Microsoft for the fix.

Q: How do I test my memory for errors?
A: Memtest86 (from www.memtest86.com)


__________________________________________________
13. GENERAL QUESTIONS
__________________________________________________


PC-133

Q:
Can I use PC-133 memory in PC-100 system?
A: Yes. All PC-133 modules will work as PC-100. Keep in mind the following:
-PC-133 CL3 may not work in a system that requires PC-100 CL2. It's best to match the latency of the module with the system's specification.
-Some systems may have a problem using x16 memory chips, or higher density 32M chips.

Q: Can I mix DDR and SDRAM together?
A: Absolutely not. Don't try this at home.

DDR

Q:
Can I use DDR-400 in a DDR-266 system?
A: DDR-400 modules are capable of running at slower speeds i.e. DDR-333 or DDR-266.

Q: Can I use DDR2 in a DDR system?
A: Nope. DDR2 is not compatible with DDR memory.

DDR2

Q:
What is DDR2?
A: Please refer to section: RAM Technology.

RAMBUS

Q:
What is Rambus?
A: Please refer to section: RAM Technology.

Q: Is Rambus compatible with DDR or SDRAM?
A: No.

LATENCY & BANDWIDTH

Q: How do I find out what my modules latency is?
A: The modules latency is normally programmed into the SPD (Serial Presence detect) chip on the module itself. There are many programs that can be used to read this. CPU-Z (from www.cpuid.com) is one of them. Using CPU-Z, you can read the SPD data from the SPD timings table under the SPD tab.

Q: What are the two most common ways in which memory bandwidth is increased?
A: Bandwidth can be increased either by increasing the number of memory channels (i.e. dual-channel) or by increasing the clock speed of the memory.

Q: How does memory access work, and what do the timings stand for?
A:
MEMORY ACCESS:
1. tRCD (RAS to CAS Delay) 2-3 cycles, The row is selected by the Memory Controller.
2. CAS (Column Address Strobe) 2,2.5,3 cycles (DDR), The Memory Controller selects the column and now the ROW is
ACTIVE, and the READ COMMAND is sent.
3. Data is sent to the DQ pins after CAS delay.
4. tRAS (Row address Strobe) 6 cycles, The module waits a certain period of time for the data to be active.
5. tRP (RAS precharge) 2 cycles, The Memory Controller DEACTIVATES the row.
6. Memory Cycle repeats as requested by the Memory Controller.

The timings are represented as follows:
2-3-2-6 1T (CAS, tRCD, tRP, tRAS)

The 1T is the command rate (see key term: command rate)

Q: How do I adjust the latency timings of my memory modules?
A: Some motherboards allow the latency settings to be adjusted in the system's BIOS. To enter the system BIOS you will need to press either the 'delete' or 'tab' key before your system starts. However, many Dell, HP, and Compaq systems do not allow for changes to the latency timings.

Q: What is the difference between 1T and 2T memory timings?
A: A 2T command rate means that commands are presented to DRAMs for two consecutive clocks, as opposed to one consecutive clock for a system with a 1T memory setting.

Q: How do I calculate my memory's bandwidth?
A:
The maximum bandwidth is calculated below for DDR-400
DDR-400 = 200MHz * 2 (double data rate) = 400MHz
400MHz * 64-bit data bus * 1bit/8bytes = 3200MB/s

Note: Not every memory bus is 64-bit. Dual-channel, for example, is 128-bit. And some older memory busses are 32-bit or 16-bit.

The calculation above assumes no latency. Of course, in the real world there is always latency. The latency add anywhere from 2 to 5 clocks per memory instruction, and is nearly impossible to calculate by hand. There are some benchmark tools that can be used to determine the bandwidth more accurately. Sisandra is one of the more popular tools:
http://www.sisoftware.demon.co.uk/san_dem/html/dload.ht...

DUAL CHANNEL
Q:
What is Dual channel?
A: See key term: dual-channel.

Q: I currently have two sticks of 512mb pc3200 memory in DIMM 1 and 3 to reach the performance of dual channel DDR. Can I also add two sticks of 256mb PC3200 in dimm's 2 and 4 to reach 1.5GB of ram and still maintain dual channel performance?
A: As long as you have matched memory pairs on each channel, you should be able to run dual channel.

The only potential problem: Because you are using 4 memory modules, which require more power, your system may clock the speed of the modules down to maintain stability.

Q: How do I know if dual-channel is working in my system?
A: An easy way to tell is to use CPU-Z (from www.cpuid.com). You can check if dual-channel is enabled by looking at the memory tab. In the General section, you will see a field labeled as 'channels #' which will indicate if dual-channel is working.

Q: Can I add 256MB and 512MB modules together?
A: Yes. Make sure you do not exceed the total memory size.

Q: Do I have to install memory in pairs?
A: It depends on your motherboard. Consult with your motherboard's manual to see how dual-channel works on your board. For most dual-channel boards the memory modules must be identically sized, and have the same number and type of chips. Typically, the motherboard requires the modules to be inserted in pairs on either slot0 and slot1, or slot2 and slot3. For some other motherboards three modules can run in dual-channel (the numbers of chips, not the modules themselves, are divided between the two channels). In any case, it is best to match the latency and speed of the modules, though it is not required.

OTHER
Q:
How much memory do I need?
A: Please refer to section: Before you purchase.

Q: How do I find out how much memory I have running in my system?
A: You can check the memory running in your system in the 'System Properties window':
START --> SETTINGS --> CONTROL PANEL --> SYSTEM.general tab under Computer.

You will see something similar to: 512MB of RAM

To check the memory setup in greater details you can use CPU-Z (from www.cpuid.com).

Q: Can I use registered memory on a desktop board?
A: No. Registered memory is only compatible with boards that support it, such as server boards.

Q: How do I find what type of memory I have installed in my system?
A: CPU-Z (from www.cpuid.com) will usually tell you the size and type of RAM from the memory section of the program.


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14. VIRTUAL MEMORY
__________________________________________________


Virtual memory is required by nearly all operating systems as a way of providing seemingly unlimited memory for computer applications and programs. It's called "virtual", because the memory is borrowed from the computers hard drive data storage.

HOW IT WORKS
As an application is executed, it normally requests a large amount of memory for its operation- much more than it typically needs just in case it may use it. So the operating systems needs to setup a PAGE FILE to accommodate the application's memory needs. The PAGE FILE contains pages (or blocks of memory) where the blocks of memory are mapped from one set of addresses (virtual addresses) to another set (called physical addresses). The physical address is typically stored on the hard drive.

WHY VIRTUAL MEMORY
Virtual memory simplifies the loading of a program for execution. Because the memory addresses are translated to the hard drive, this eliminates the need for memory addresses to be stored in one long continuous block. The operating system only needs to find a sufficient number of pages in the main memory.

PAGE FILE OPTIMIZATION
Q:
How to check page file size set by windows?
Windows will set the page file size automatically. You can check it by using DirectX Diagnostic Tool:
START --> RUN --> "dxdiag" and hit ENTER
Q: How to check the peak amount of memory since my last boot?
A:
1. Open the Windows Task Manager (CONTROL + ALT + DELETE)
2. Look under Performance tab at the Peak value.
It is best to record the peak value over a period of time, and just not assume that any single reading is the peak. After a period of review, you can easily determine what page files size if right for your computer.

Q: How to change the Page File Size?
A: The recommended minimum page file size is about 1.5 times the amount of RAM in your system, and the maximum recommended is about 3 times. By default windows will set this value for you. However, you can determine using the steps above what page file size is best for your system and change it manually:
START --> SETTINGS --> CONTROL PANEL --> SYSTEM --> ADVANCED --> performance.SETTINGS --> ADVANCED --> virtual memory.CHANGE


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15. MANUFACTURERS
__________________________________________________


There are a few top-rated memory manufacturers out there, who do the right thing in making memory that works. These are companies that work closely with CPU and motherboard manufacturers as new machines are being developed, and make sure that all of their modules are following the standards set in their specification.

Manufacturers are typically the best source for memory modules in that they offer better terms of service and returns for their products than the brokers or middlemen. Good service typically comes with lifetime warranty, and knowledgeable staff who can answer specific questions relating to the technology and respective applications. Companies that work closely with the manufacturers and distributors are the best source for memory modules.

Because Manufacturers and good vendors take extra steps to ensure the service and quality of their memory, the prices may be a little higher than buying from a broker or middleman. The extra price is probably worth it given the extra care and support that comes with it.


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16. BROKERS
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A broker is typically an individual who works with memory manufacturers and distributors in negotiating purchases, contracts or sales in return for a fee. Little to no value is added to the product, but instead the broker is looking to mark up and move out the product at a profit. Because there are many brokers in the memory market, it sometimes becomes very difficult to tell the brokers apart from the dedicated distributors.

There is very little regulation over the products in the memory market and so the level of quality can vary significantly from product to product- at times you may not even know what you are getting until you receive it. And because it is normal for products to trade many hands before they are consumed, the prices are very inconsistent.


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17. COUNTERFEIT MODULES
__________________________________________________


What is Counterfeiting?
Definition: The deliberate attempt to deceive product purchases by copying and marketing goods bearing well known trade marks, generally together with packaging and product configuration, so that they appear to be made by a reputable manufacturer when they are, in fact, unauthorized and generally inferior copies.

Why is it bad?
There are many reasons, but most importantly a counterfeit module is always inferior in quality to the product it intends to be.

How do I identify a counterfeit module?
Any reputable manufacturer can easily identify a counterfeit module. But for the average consumer, it is not so easy. There is, however, one easy technique that can be used to identify a module as counterfeit. The normal counterfeiting process involves re-marking of memory chips after the module is assembled. Normally, the chips are marked prior it its assembly. This means, that the markings of each chip on a counterfeit module are identical and the markings from one chip to the next are perfectly aligned in a straight line. The real modules normally come with different markings per memory bank and the markings from one chip to the next are not perfectly aligned. This is just a general technique and should not be used to confirm a module as counterfeit.


__________________________________________________
18. RAM GUIDES
__________________________________________________


http://www.corsairmicro.com/memory_basics/153707/index.html CORSAIR

http://www.kingston.com/tools/umg/umg.pdf KINGSTON: The Ultimate Memory Guide

http://www.ocforums.com/showthread.php?t=308361 OC FORUMS

http://www.anandtech.com/memory/ ANANDTECH

http://www.tomshardware.com/motherboard/index.html TOMS HARDWARE GUIDE


******
"My Memory is not working today"
AIM SoCaliCrowley
January 6, 2006 1:43:13 AM

I recently bought a large quantity of 500 celeron boxes w/o optical drives, HDs, or ram on Ebay Here. The specs state that the ram operates @ 100Mhz. I once bought a 256 stick of "pc 133 only" at circuit city, years ago. I still have it, and it has failed to work in any pc 100 slot (granted most were mostly oem's like dell, hp, et al).

Now I’m in the market for a lot of ram, and I’m concerned that I may get a large lot of completely incompatible stuff that will be useless to me. Any tips for me?
How do you tell High density from low density (high density has less chips per meg???)

I'm anxious to get my folding farm up and running :) )

Thanks in advance
Related resources
January 6, 2006 2:11:20 AM

nice thread, very informative & comprehensive at the same time.
January 13, 2006 11:53:18 AM

Great post! I like to optimize the pagefile whenever I build a system. The two main issues are pagefile fragmentation and the resources that the PC uses if it needs to expand the pagefile.

For the first one, after I build up the system, I will set it to use NO pagefile, then reboot. This will clear out the disk space that the pagefile uses (you can see it if you analyze using Defrag). When it comes back up, I set the pagefile to exactly what I want (see below). This makes sure that the pagefile is contiguous and situated optimally (not split between 2 or more places on the drive as you can often see using defrag).

The second issue, is setting the pagefile to a single size (min and max set to the same value). This way, you don't get a performance slow down from Windows automatically resizing the pagefile. It also prevents pagefile fragmentation in conjunction with the step above. As for size, I usually set it to twice the physical RAM. I've never had an issue with running out of virtual memory at this setting. If you find you are, or you add more RAM, you can always set the pagefile to 0, run degfrag, then reset your pagefile to a higher value.
February 8, 2006 2:19:19 PM

Don't forget Crucial; they have an excellent system identifier to pick the correct RAM for a machine without opening it up (great when I'm at friends' or clients') and several good pages of information about RAM in general.

Crucial is notably a division of a RAM manufacturer themselves, and they guarantee all their RAM for the life of the machine.
June 23, 2006 9:08:11 AM

thanks man you have done a great service to new people learning about and some conceptual doubts
keep posting such impressive and comphrensive
June 23, 2006 8:55:26 PM

ahaha i posted before reading
October 9, 2006 10:37:39 PM

Does anyone know where i can find a more detailed tutorial?
I am interested particulary in the phisical layout of the memory chip and how exactly the address and control signals work together to select a memory location. Use technical terms, i'm not affraid of them :)  . thanks
December 29, 2006 1:29:39 AM

GREAT INTRO! I LIKE IT!!!

the comments about chip density falls into the common misunderstanding trap of why high density chips don't work in older systems. the root cause is REFRESH! the RAM is not refreshed the same in newer systems.

i have worked in memory developement for many years. please see my ebay guide to find out more detail about this problem.

http://reviews.ebay.com/PC133-MEMORY-COMPATIBILITY-ISSU...

keep up the good work. bobvc99
December 29, 2006 2:20:15 AM

Very nicely done.Good research and knowledge base is good to have for anyone,even experts.

Dahak

AMD X2-4400+@2.4 S-939
EVGA NF4 SLI MB
2X EVGA 7800GT IN SLI
2X1GIG DDR IN DC MODE
WD300GIG HD
EXTREME 19IN.MONITOR 1280X1024
ACE 520WATT PSU
COOLERMASTER MINI R120
February 13, 2007 5:50:44 PM

Hi.. I'm not memory expert (that's why i wondered in here)..
I came here wondering how the CL-timings are compatible on systems with lower speeds: ie. PC2-5300 CL-5 memory on PC2-3200 CL-3 system.. at first, looking at the numbers it seems like that wouldn't be a good match (slower CL-5 chip on motherboard supporting PC2-3200 CL-3).. but then..

In your post I found it interesting to see standard JEDEC timings for different memory speeds:

9. TABLE OF STANDARD SPECIFICATIONS (WITH LATENCY)
DDR2
DDR2-400 = PC2-3200 (200MHz @ CL=3, tRCD=3, tRP=3)
DDR2-533 = PC2-4200 (266MHz @ CL=4, tRCD=4, tRP=4)
DDR2-667 = PC2-5300 (333MHz @ CL=5, tRCD=5, tRP=5 OR 4-4-4)
DDR2-800 = PC2-6400 (400MHz @ CL=6, tRCD=6, tRP=6, OR 5-5-5)

It says that faster memory has to wait more clock cycles to respond (at faster speeds).. well.. I plugged it into spreadsheet and..
look at that:

Memory type/speed -- CL -- CL divided by speed [Mhz]
PC2-2600 - 333 - 166.5 - 2.5 - 0.015015015015015
PC2-3200 - 400 - 200.0 - 3 - 0.015
PC2-4200 - 533 - 266.5 - 4 - 0.015009380863039
PC2-5300 - 667 - 333.5 - 5 - 0.014992503748126
PC2-6400 - 800 - 400.0 - 6 - 0.015

Hey! CL/speed is CONSTANT (0.015)!!! (the actual 'phycial' time it takes memories to respond is THE SAME!)
In real terms it means that standard memory PC2-5300 CL-5 will respond in the same time as PC2-2600 CL-2.5..

That would mean that I can upgrade with faster memories with LOWER CL values.. to the level listed above.. of course considering other compatibility issues.. like too high density (not supported by motherboard).. etc..

I checked it for the PC2 memories I was interested in..

I'm not memory expert so.. please tell me if there's something wrong in my thinking..

Hope this may be useful to someone..
February 23, 2007 3:59:48 AM

Quote:

<b>Q:</b> <i>How do I calculate my memory’s bandwidth?</i>
<b>A:</b>
The maximum bandwidth is calculated below for DDR-400
DDR-400 = 200MHz * 2 (double data rate) = 400MHz
400MHz * 64-bit data bus * 1bit/8bytes = 3200MB/s

Note: Not every memory bus is 64-bit. Dual-channel, for example, is 128-bit. And some older memory busses are 32-bit or 16-bit.


The note implies that that DDR-400 dual channel capable memory would be shown as PC6400, but I think it is not the case. I am not 100% sure but I think that the memory card itself is still called PC3200 but you can use two of them in dual channel configuration.
February 23, 2007 1:18:42 PM

Quote:
The note implies that that DDR-400 dual channel capable memory would be shown as PC6400, but I think it is not the case.

I am not able to follow your reasoning here as I don't see that the note implies that. The theoretical maximum bandwidth associated with a dual channel capable motherboard using two PC3200 DDR DIMMs would indeed be 6,400MB/s. But the individual memory DIMMs would still just be PC3200.

Dual channel is a not an attribute that is associated with a memory DIMM. It is a capability of the motherboard/chipset, not of the memory itself. No?

-john, the ostensibly clueless redundant legacy-in-transition dinosaur
February 23, 2007 10:00:08 PM

That what I am kind of saying. I think the confusion is that the question does not specify which "memory bandwidth" it calculates. It could be memory module bandwidth, as I initially understood, but of cause he means memory bus bandwidth.
June 9, 2007 1:18:08 AM

DDR2 RAM Chip List

If you go up a directory the guy has a few other good lists, but that one I found to be the most vital.
July 11, 2007 4:14:57 AM

@shk:

Thanks for that list it very helpful.

f61
July 11, 2007 4:40:58 AM

:hello:  So far this is a great thread, and I have a few more questions concering memory latency.

On some newer MoBo's there are advanced settings that when one goes to manual settings aren't so obvious as to their definition. Some of these are not posted here, but are set to a default that might not be proper. So as to be complete, I'll list all that I can see under BIOS for a BioStar TF7025-M2 MoBo. Bear with with me, as a few of these are posted here in OP.

TwTr = 1,2,or 3 (Command Rate?)
Trfc (for each socket DIMM 0 1 2 3) 75, 105, 127.5, 195, 327.5 (nano second I presume)
Twr = 3,4,5,6
Trtp = 2 or 3
Trc = 11 to 26
Trcd = 3,4,5,6 (2nd #)
Trrd = 2,3,4,5 (CAS?)
Trp = 3,4,5,6 (3rd #)
Tras = 5 to 18 (4th #)

I'm new to this, but trying to learn, and convert to the BIOS list.
Will CPU-Z show me all of the latencies, or just the important ones like CAS,Trcd,Trp,Tras,CMD. Its tough to know how to configure the rest of the numbers not in the thread, or decipher whats going on, or the interrelation to the major 5.

Thanks for the enlightenment.

f61
July 29, 2007 10:43:25 PM

fault
August 25, 2007 3:09:03 PM

Thank you both Brent and Hatman.

FAQ's like this are great, but work best when legible. :) 
September 4, 2007 6:26:46 PM

i have 1 gig of corsair ram 2 512mb sticks in the ist 2 mobo slots...
and its running at 128bit dont know what that means anyway i shoved in a new gig of ram then it was running at 64 bit plus when loading up pc it would freeze and my comp would crash...can anyone help with this...would me shoving in the new gig of ram in to 2 4th memory slot have caused this..any help would be gratefull
September 5, 2007 6:48:32 AM


I would like to ask, but sorry if my question inrelevant with the topic here.

Ihave Elpida 1Rx8 PC3200R-333 Memory, it was working well on my
HP Proliant Server but when I pluged it to my PC (Asus P5LD2-VM)
it could not boot and the bios did not appear at all.
Does my Elpida only work well on servers ?
Please help. TX


fay
September 18, 2007 9:02:41 PM

not sure about ya'll but i am seeing the all the HTML markup and it makes it a pain in the arse to read
October 4, 2007 5:56:59 AM

Looking forward to the Best Bang for the Buck memory articles. Would also like to see a similar column on Power Supplies. Maybe not monthly, but quarterly would be nice.

It would also be nice to see a blurb on Geil memory. Due to their high prices, I generally avoided them, but I always heard it was good stuff. Now they supposedly want to play in the mainstream as well with lower prices.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
October 5, 2007 12:37:32 AM

Interesting introduction, but I thought tight timings simply meant low latencies. You state that combining them costs the most. Could you flesh that part out a bit?

Thanks!
October 5, 2007 2:30:56 AM

Job well done.

October 5, 2007 3:27:28 AM

Nice guide, THG needed one.

F61, here is something to play with MemSet memory tweaker. The settings are only temporary for tweaking they are gone on reboot. There is additional information in the thread. I don't have these settings worked out by any stretch. I spent a little time on it, but it's hard to sort it all out. I guess I need to spend more time on it. If you, or anyone else, gets them sorted out post the info.
October 20, 2007 1:13:36 AM

Hello guys....i'm not sure if i'm posting in the right. If i am, i do apologize. I'm very new in building PC and i just built one..but have a problem. I have no idea how to set my memory timing.

My stuff:
AMD64 x2 6000;
XFX GeForce 8800GTX
Crosshair Mobo
Mushkin memory (soon to be received by mail on Monday)

I've asked Mushkin on what the settings are and he provided but when i went into BIOS, doesn't seem to match. Can somone help me on this particular problem? Much appreciated. Here is what the settings are:

Set memory clock to 800Mhz divider.

Command Per Clock: 2 CLK
CAS Latency Control: 4 CLK
Min RAS Active Time: 10 CLK
RAS to CAS Delay: 4 CLK
Row Precharge Delay: 3 CLK

If sub timings doesn't work , try changing these.

RAS to RAS Delay: 3 CLK
Row Cycle Time: 11 CLK
DIMM 1 Row Refresh: 75ns
DIMM 2 Row Refresh: 75ns
DIMM 3 Row Refresh: 75ns
DIMM 4 Row Refresh: 75ns
Read Precharge Time: 2 CLK
Write Recovery Time: 6 CLK
Read to Write Delay: 4 CLK
Write to Read Delay: 3 CLK
Refresh Period Time: 3.9us

Memory Voltage - 1.9 to 2.1V

Thanks again...
November 2, 2007 8:52:39 AM

I have 256mb ram in my system. but shows 31 mb ram.
what is reason
November 20, 2007 12:46:40 AM

I have a 2X1024 800MHz DDR2 Gskill memory.
When I check with EverestUltimate it reports an effective speed of 743.
Other parameters are
CPU Speed:
CPU Clock 2599.9 MHz (original: [ TRIAL VERSION ] MHz)
CPU Multiplier 13.0x
CPU FSB 200.0 MHz (original: 200 MHz)
Memory Bus 371.4 MHz
DRAM:FSB Ratio CPU/7

In the benchmarks it shows consistantly lower performance than a 800MHz memory system.
I am using defaults in the BIOS of my Asus M2A-VM HDMI board with AMD athlon Dual core 5000+ Brisbane CPU
Why do I get this lower values?
December 22, 2007 6:13:26 PM

so if i bought 2x1gig of black dragon pc6400 memory..then sometime later i bought another set of the same i wouldnt have any problems doin this
January 1, 2008 7:37:04 PM

this thread could do with an update, since ddr3 is out now....
January 20, 2008 12:16:44 AM

So how would u distinguished the d-9 chip to generic chip.... I do see some generic rams with good timing.....
January 20, 2008 12:23:40 AM

"BRAND OF MEMORY
A: You can normally find the brand by looking directly at the modules themselves. If no sticker, label or logo exists on the module, sometimes you can find the brand labeled on the chips."

Is this means you going to buy something that you don't even know and removing the cooler is not usually easy and can void warranty....
January 23, 2008 5:25:30 AM

February 14, 2008 5:56:14 PM

Thanks for the infor. Am new to this and stiil haveave a question. Have a Dell Precision Wkstation 340 with PC hardware w 2 x 256 Rambus Memory PC 800 - 40 ECC Dell Ram. Would it be ok for the system to add 56 mb (2X128) Rambus Memory PC 800 - 45 ECC Dell Ram for additional ram memory. Thx...
February 22, 2008 6:17:47 PM

Howzit this is for anyone to reply to;

I'm looking for the BIOS settings to clock two 1gig DDR2 1066 Kingston KyperX's ,at 1066MHz (auto. clock at 800), I got the ASUS Max. Formula board and it's not accepting the simple clocks... has anyone got a similar board?? or knows the latency's??
a b } Memory
March 9, 2008 11:43:37 PM

^Post in new topic.
a b } Memory
March 9, 2008 11:57:10 PM

@OP:

More on COUNTERFEIT MODULES.

You can also find out if the RAM is counterfeit by running CPUZ. Under "SPD" you can select the RAM slot that you have installed the RAM in and then checking the value for "Manufacture" , "Part Number" and the "Module Size". If one or more of these values are not correct there is a very good chance you have been ripped off.
April 10, 2008 4:02:51 PM

Quite a useful information at first.

I am thinking to upgrade my RAMs, from 2x533Mhz DDRII (1GB each) rams, to 4xDDRII (1GB each) of RAMs. But I am not sure if it is better to get 667MHz or 800MHz with Quad Core Q6600 2.4GHz with Intel 975xbx2.

Any help please?
April 11, 2008 1:20:34 AM

should go for the 800 stuff its like $1-5 between each ram speed type

your ram would most likey be holding your pc back with 533 1gb used (can you even buy 533 1gb ram?)

----------------------
topic could do with been an small update to reflect that you need an 64bit OS to use 4gb of ram fully and state that 32bit os depending on how many video cards are used (and some other things as well) can result between 3.5gb down to 2gb of useable ram on an 32bit OS
April 11, 2008 5:42:29 PM

Thanks for the help leexgx, I decided to go for the 800MHz of RAMs.
April 24, 2008 2:54:54 AM

I get really good deals on those DDR pc2700 memory chips on roaminggear.com. They also sell cheap new and used laptops. The crazy thing is how little computers use the pc3200 memory but the DDR kind. The DDR2 kind is literally worthless, you know it is. At roaming gear the mobile laptops new ram cost about 35 dollars for a gig chip. I was lucky since I had a gig per slot laptop. I mean 35 dollars for new 2 one gig chips. But thats making a medium grade computer completely overhauled and faster.
June 9, 2008 7:39:50 AM

Nice piece of info.
July 5, 2008 11:59:31 PM

In the Key Terms section:

"Semiconductor: A material such as germanium or silicone..."

Please replace the word silicone with silicon.

I cringe every time I hear engineering students confuse these two words.
October 9, 2008 3:20:10 AM

wow man great post. Kudos!
a b } Memory
December 8, 2008 6:42:09 PM

Correction needed:
BrentUnitedMem said:
Memory module bank: Logical division of chips on a PCB board. A single memory bank can be composed of any number of chips. Some banks are composed of only 2 chips, whereas some other modules have 18 chips or more per bank. Not to be confused with memory Rank, see next term.
Memory rank: The physical side of a memory module. The side of the module is referred to by Rank0 or Rank1.

Actually, DIMM rank is a logical 64-bit memory side (chip-select), synonymous with one 64-bit memory row. JEDEC adopted the term "rank" specifically to address on-going confusion between physical and logical memory "sides".

Case in point, unbuffered DIMMs using 4-bit wide DRAM IC (32Mx4, 64Mx4, 128Mx4, et. al.) will have 16 chips total, eight on each "physical" side, but are in fact only single-rank modules. These are commonly referred to as 'high density' modules, though the term 'high density' is entirely relative and can have different meanings depending on the technology or context being discussed. Another example are registered server DIMMs, which can have up to four (quad) ranks per module, two ranks on each "physical" side.
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