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HELP!!! DIMM TROUBLE!

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February 5, 2007 8:59:24 AM

is a single 1gb ddr2 module better than two separate ddr2 512mb(dual channel) ??
is there any difference in performance?


i looked at some rams.. and found most of them with 667 where pc5400 (like listed in the guide), and some of them the pc2-667 but pc2-5300 not 5400!.. whats the difference, and how does this have an effect on performance?

.. so far after going thru the corsair review.. i found out that registered rams are better, and so are ECC rams... ?

what do u think is good for performance?

and last which manufacturer is better, kingston, corsair or ocz?

More about : dimm trouble

February 5, 2007 9:51:14 AM

2 seperate 512MB DDR2 modules in Dual Channel will be twice as fast as a single 1GB stick.

DDR2 XXX and PC2-XXXX is a measure of ram speed, im sure you can find info on this if you look on the net.

PC2-5300 = 667MHz
PC2-6400 = 800MHz etc..

basically the faster the ram, the faster stuff will load. CAS latency is another important factor, for DDR2 ram you ideally want timings of 4-4-4-12 or lower, depending on the speed of the RAM, Registered DIMMs only work with certain CPUs and Motherboards, and usually cost more.

Corsair is arguably the best RAM manufacturer, but OCZ and Kingston also make reliable ram. Lastly RAM is a acronym. That is, it has no plural.
February 7, 2007 8:40:58 AM

lol im confused.. how come there are ddr2 modules, which are PC2-xxxx as well as PC-xxxx?? whats the difference between these two?

theres ddr2 667 modules which are PC2-5400 and PC2-5300?? whats the difference between these two?

and theres ddr2 677 modules which are PC-5400 and PC5300?? whats the difference between these two?



Which of these combinations below exist, and how can u identify them - when i was researching it only mentioned the modules were "non ECC" and/or "unbuffered", none of the modules mentioned they were buffered or had ecc or was registered.. so now i have doubts :p 

non ECC, unbuffered
non ECC, buffered

ECC, unbuffered
ECC, buffered

non ECC, unbuffered, registered
non ECC, buffered, registered

ECC, unbuffered, registered
ECC, buffered, registered

for desktops which are the types used?

appreciate your help.. thanks
Related resources
February 7, 2007 9:19:49 AM

Quote:

2 seperate 512MB DDR2 modules in Dual Channel will be twice as fast as a single 1GB stick.


No, they'll not.
Dual Channel gives you a 5% performance boost over single channel.

If you plan to go to 2GB of RAM in the near future, buy 1 stick x 1GB now, so you can dual channel then. If not go for a dual channel setup now.

DDR2 nnn goes with PC2 nnn*8
DDR nnn goes with PC nnn*8

So DDR2 667MHz gives you PC2 ( 667*8 ) = PC2 5336 which is rounded to PC2 5400 (or 5300)
February 7, 2007 11:18:04 AM

Quote:
No, they'll not.
Dual Channel gives you a 5% performance boost over single channel.


I don't care about arguing, however. The peak bandwidth of ram is calculated as:

Memory Speed x Number of bytes transferred per channel x Number of Channels

which can be read here, in infineon and kingston's white paper on Intel Dual channel architecture. http://www.kingston.com/newtech/MKF_520DDRwhitepaper.pd...
If that info is wrong, take it up with the writers.
February 7, 2007 12:37:55 PM

Teoretically, Dual Channel doubles the memory bandwidth.
That doesn't mean, however, that the memory is twice as fast, nor that the computer will be twice as fast.
The overall performance increase when using dual channel is around 5%, because the CPU doesn't use 100% of the memory bandwidth.

PS. That white paper is old, though it's good for a simple explanation.
February 7, 2007 11:05:34 PM

Quote:
Teoretically, Dual Channel doubles the memory bandwidth.
And also in practice.

Quote:
That doesn't mean, however, that the memory is twice as fast,
Yes, it does. It means the bandwidth is doubled between the memory and the memory controllers (northbridge (Intel) or CPU (AMD))

Quote:
nor that the computer will be twice as fast.
Correct. Many things influence the speed of a computer besides the memory bandwidth, including CPU, hard drive, amount of RAM, graphics card, etc.

Quote:
The overall performance increase when using dual channel is around 5%,
Sounds reasonable, but this can vary dramatically with CPU, MB, apps in use, etc.

Quote:
because the CPU doesn't use 100% of the memory bandwidth.
Not really. It's because the CPU doesn't spend all of its time reading/writing large blocks of memory. When it IS reading/writing large blocks of memory, the CPU does use all the memory bandwidth, up to the limit of the memorycontroller <-> CPU bandwidth.
February 9, 2007 6:16:32 AM

non ECC, unbuffered
non ECC, buffered

ECC, unbuffered
ECC, buffered

non ECC, unbuffered, registered
non ECC, buffered, registered

ECC, unbuffered, registered
ECC, buffered, registered

hey guys come on.. stop arguing (if not.. im sorry).. and help me know if theses DIMMs even exist?

and one more thing: is it the mobo that provides dual channel or is it both the mobo and the DIMMs that has to be dual channel, in order for dual channel performance? (because when i researched DIMMs, i found that some pairs for example 2x512 have nothing written on them and some with dual channel written on them)?

and.. if i have a 1gb stick, and a 512mb stick (1.5gb)? how would the system performance be? would it work in dual channel?

if i got 3 512mb DIMMs would it all work in dual channel or only two of them would?
February 9, 2007 7:06:59 AM

Quote:
non ECC, unbuffered
non ECC, buffered

ECC, unbuffered
ECC, buffered

non ECC, unbuffered, registered
non ECC, buffered, registered

ECC, unbuffered, registered
ECC, buffered, registered

hey guys come on.. stop arguing (if not.. im sorry).. and help me know if theses DIMMs even exist?

and one more thing: is it the mobo that provides dual channel or is it both the mobo and the DIMMs that has to be dual channel, in order for dual channel performance? ?


All memory that anyone is using in your regular run-of-the-mill home computer or gaming system is non-ECC, unbuffered, that's all you have to worry about. ECC (Parity checking) is used in business systems where data integrity is paramount; buffered ram is used in Servers and requires an expensive supporting chipset.

All current AMD, ATI, Intel, and Nvidia desktop chipsets support dual-channel DDR/DDR2, as do most new laptop sets. You put two similar sticks in the paired slots and the memory bandwidth is doubled, increasing performance during operations that require a lot of memory paging. One stick can however be used in any modern set, and frequently just one stick is used for testing and troubleshooting. The obsolete Rambus standard, used in early P4's, required all four slots to be filled, a matched set plus dummy bridges or another matched set.

DDR = PCxxxx, and is being phased out in favour of DDR2 = PC2-xxxx and evenutally DDR3. DDR(number) times 8 = PC(number) eg. DDR400 X 8 thus = PC3200. DDR2-533 = PC2-4200 (4264) DDRx designations are becoming the preferred method rather than PCxxxx.

Latency is VERY important, and is what is improved in more expensive ram, rather than just raw speed. 5-4-4-12 etc. is a latency designation for DDR2. CL3 is average for DDR, CL2.5 is very good, CL2 is enthusiasts. DDR2 has higher (slower) latencies than DDR because it does more work per clock cycle, but high-end DDR2 is now bringing latencies down to the levels of DDR.
February 9, 2007 8:04:47 AM

Welcome to the forum woof :) 
http://www.webopedia.com/quick_ref/dram_memory.asp
That will intro you to the terminology and what it means. Some games love(need) the extra bandwidth of dual channel but intensive programs like video editing apps really benefit from it.
The other problem is that you run a higher risk of incompatibility if you buy 1gb of memory now and then another 6 months from now. Dual channel memory has to be identical to run dual channel. Thats why you see sets of DIMMs sold. Memory can be sold under the same brand name and capacity but can use varying PCBs or memory chips. It can be hard to get a perfect match.
February 9, 2007 11:44:59 PM

Quote:
... Dual channel memory has to be identical to run dual channel. ...

This used to be common, but the most recent chipsets are more forgiving. The latest Intel chipsets will even allow modules of different capacities to run in dual-channel mode (e.g. 1x1GB in one channel and 2x512MB in the other channel).
February 10, 2007 6:20:09 AM

You cannot maintain dual channel without two DIMMs in a channel. Yes you can have different sizes but there has to be two DIMMs for each used channel. 2x 1gb plus 2x 512 would work and the like, but you do have to have identical DIMMs in each respective channel and you must have 2 per channel for dual channel. :)  I am open to reading any links you can give me that will prove otherwise :wink:
February 10, 2007 10:24:29 AM

Quote:
You cannot maintain dual channel without two DIMMs in a channel. Yes you can have different sizes but there has to be two DIMMs for each used channel. 2x 1gb plus 2x 512 would work and the like, but you do have to have identical DIMMs in each respective channel and you must have 2 per channel for dual channel. :)  I am open to reading any links you can give me that will prove otherwise :wink:


Why do you keep saying "identical?" They should match for latency and base speed so that the slower ram does not disallow the other ram from reaching its rated speed. And matched slew rates does make for better stability when overclocking, they probably both have to be either single or double-sided, but two sticks working in dual-channel do not have to be "identical."

My Athlon 64 3200, on an RDX200, slightly overclocked, is using two DDR400 1 Gig sticks in dual channel; one is a Corsair Value Ram, the other is a Kingston, each using different brands of chips but both CL3. The system is as stable as a rock.
February 10, 2007 6:57:40 PM

Quote:
You cannot maintain dual channel without two DIMMs in a channel.

Of course you can. Just put one DIMM in each channel, and as long as they meet the chipset's requirements, they'll work in dual channel mode. This is the mode that most people use (e.g. 1x1GB in channel A and 1x1GB in channel B).
Quote:
Yes you can have different sizes but there has to be two DIMMs for each used channel. 2x 1gb plus 2x 512 would work and the like, but you do have to have identical DIMMs in each respective channel ...
Quoting myself from my post above :wink: "This used to be common, but the most recent chipsets are more forgiving." Here's the first reasonable link I found: http://www.intel.com/support/motherboards/desktop/sb/cs...

The latest Intel chipsets even have a hybrid mode for situations where the total amount of RAM in each channel is different. For the greatest common amount, they run in dual-channel mode, and only run in single-channel mode for the "excess" RAM in the one channel. For example, if you have 1GB in channel A and 2GB in channel B, the first 1GB of each channel would run in dual-channel mode, while the "excess" 1GB in channel B would run in single-channel mode.
February 11, 2007 1:28:40 AM

You just hit the nail right on the head. :D  Dual channel needs two DIMMs. That hybrid mode is pretty cool but as you said does run 1 DIMM in single channel mode. When I referred to each channel I should have been more clear. The motherboard manual indicated which slots are to be populated with one dimm in each slot for Dual channel mode. I did not make myself clear on that sorry :lol:  I called the pair of slots a "channel" when it is actually one slot from each respective channel. I should have phrased it differently.
February 11, 2007 1:42:45 AM

Running two different brands is difficult without potentialy defaulting to single channel mode. Thats why I keep saying identical. Those DIMMs you have must have been manufactured to the same overall specs. Unfortunately,not all DIMMs are.
February 11, 2007 2:41:31 AM

pax, it varies a lot between chipsets. Like I said, the latest Intel ones are VERY tolerant, so different brands are very unlikely to cause problems on such MBs. If 1x1GB in one channel and 2x512MB in the other channel will work, it's hard to imagine modules of the same size not working.
February 11, 2007 2:52:34 AM

True and the link you supplied does clearly state that the memory doesn't need to be the same brand. I guess I just like to be sure. 8)
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