Some Memory Basics
Advertisements usually only talk about the capacity of memory installed on systems: 1 GB, 2 GB or sometimes even 4 GB, although anything at 4 GB and above requires either a 32-bit operating system capable of handling the memory addressing to take advantage the memory capacity, or a 64-bit operating system, which natively supports much more RAM. Any system running Windows XP or Windows Vista should at least have 1 GB of memory. On the one hand, this will prevent Windows from swapping too much work data onto the slow hard drive. On the other hand, RAM has become really inexpensive, making memory one of the most affordable components.
Memory is always added to a system on so-called modules. Desktop PCs utilize Dual Inline Memory Module (DIMMs), the “dual” means that there are pins on both sides of the connector. Memory chips can also be located on both sides of a module. The first DIMMs had 168 pins and were used for SDRAM memory. The second generation for double-data rate RAM (DDR) had 184 pins, while the current DDR2 and DDR3 DIMMs have 240 pins. Differently positioned notches prevent users from confusing DDR2 with DDR3.
Due to space constraints, notebooks and laptops utilize different memory modules, which are called Small Outline DIMMs (SO-DIMMs). These are roughly 1/3 of the size of regular DIMMs, and have only 200 pins. Most notebooks offer two sockets for SO-DIMMs, although ultra-portables oftentimes come with permanently installed memory and only one slot for upgrades.
It’s important to know that the best performance is achieved by pairing two physical memory banks, which are referred to as channels. All memory controllers, whether they’re integrated into an AMD Athlon 64 X2 or Phenom X3/X4 processor or part of a chipset northbridge, are capable of running dual-channel mode, which means that they utilize two banks in order to double the bandwidth by widening the memory data path from 64 bits to 128 bits.
Good RAM, Bad RAM
While memory is categorized by memory type (DDR2, DDR3) and memory speed (clock speed), there are also various parameters that need to be set, called timings, and they’re also relevant to performance. However, the performance difference between mainstream memory and high-end RAM has been rather small. It is highly important to use a reasonable memory technology, which currently is DDR2-667/800 for notebooks and DDR2-800/1066 for desktop PCs. Running fast memory timings is favorable, but we recommend against spending a lot of money on enthusiast memory unless you’ve already optimized other key components such as the processor or the graphics card. In the case of notebook memory it’s usually not possible to alter memory timings anyway.
Mix or Match?
Memory vendors try to sell so-called matched memory pairs, which are often tested together in a standardized test environment. While two different DIMMs with identical specification should technically work together, issues may occur. Huge compatibility problems, resulting in functional incompatibility, are very rare these days, but it’s fairly possible that RAM speed or timings may have to be adjusted to slower settings for compatibility reasons.
You can always operate any memory type at slower clock speeds and more conservative timings than they were specified for. Running a DIMM above the specification, though, puts you into the overclocking corner, and must be done at your own risk. If you mix a 1 GB DDR2-667 and a 1-GB DDR2-800 DIMM, both will run at DDR2-667 speed.
I like the review and have noticed a better system, especially with vista 64 but wish we could get even more right now.
The problem with getting 'even more' is that most notebook motherboards are not made to deal with more than 4GB's memory.... in fact, I think I read that there was a problem with desktop motherboards before the latest ones when you tried to put in more than 4GB's memory.
I can for some part prove that battery life does go up with 4gb of ram. I have an older Toshiba A105-S4094 which has a Centrino Duo (pre Core 2 tech) T2250 @ 1.73Ghz. It came with 1.5GB (1 X 512mb 1 X 1Gb)that I later upgraded to duel 2gb sticks. It is only 32bit atm and pre SP1 Vista Ultimate (so it only sees 3gb) but with what I have, I disabled the swap file and run most everything just fine. Performance did increase a bit and my battery life went up about 30min or so when in power save mode with wireless on during my long late classes. I would think that having the harddrive shuffle less would definitly cause the battery to last a bit longer and well looks like my hunches were right.
very nice, but i'll stick with 2 GB ram
"...at the German price comparison platform...." It is a AUSTRIAN platform. Let them be pride of something...
Who in their right mind would leave virtual memory enabled? The most I've ever used is roughly 1.4GB in XP though Vista will cache things immediately after it's installed without knowing what I'll actually bother to use. This is just as bad as virtual memory!
I'll stick with XP and my 2GB of Corsair until a version of Linux that doesn't require you to wander in to the console every five minutes comes along.
...one nice thing though is that the reviews consider reasonably priced equipment. I don't care about 8800 Ultras, 9800GX2s, or thousand dollar CPUs. I've got more important priorities then trying to impress people who aren't getting any work done.
This may seem like a silly question, but at the rate which SSHD's are gaining capacity and speed wouldn't that make DDR memory a thing of the past? At least i hope there will come a point in which read and write times to/from a SSHD would be as fast as the latest DDR2/3 memory and beyond. And if SSHD could achieve such speeds i think it would be completely possible to remove system memory and partition of a section of the HD to serve as the systems memory. And in the event that one could do this, one could easily adjust the memory as needed. The only limitation that i see would be in the operating systems ability to handle "x" amount of memory. Now this may not work at all, but it was a thought that had occurred to me while i was reading the article.
Lets explore that thought shall we.
The fastest SSD I've seen has read/write speeds of approximately 110MBps/80MBps and an access latency of about 0.1ms.
If significantly faster SSDs are currently for sale, please forgive me for not keeping up with storage tech the way I used to. (BTW, FusionIO is neither an SSD nor affordable outside of datacenters)
To simplify things we'll just use the faster of the two.
110MBps = 880 Mbps
This is roughly the effective throughput of single channel DDR-400 on an AthlonXP chipset. (Memtest86(+))
It is a little more than half the effective throughput of the single channel DDR-400 controller on the socket 754 Athlon 64 systems.
It is less than a quarter of the effective throughput of the dual channel DDR2-800 controller on an Athlon64 X2.
I don't have readily available numbers on an Intel DDR3 system, but you can see where this is going.
(I could have put in Intel memory controller results and/or AthlonXP dual channel results, but these numbers fit better to get the general feel of things)
These results aren't bad actually.
SSDs may not have reached even the last generation of memory technology, but at least in throughput, they match RAM technology that was widely used to run Windows XP.
Side note: If you use theoretical bandwidth, then SSDs can't reach DDR-400 (3200Mbps) until the interface gets upgraded to 4GHz (~400MBps).
If the numbers seem funny to you, it's because I'm taking into account the 10/8 encoding scheme that SATA uses.
The real kicker is the access time.
0.1ms seems very fast in HDD terms, but on a 2GHz processor, this is about 200000 cycles of latency.
Compare that to:
150-165 cycles for the AthlonXPs
125-140 cycles for P4s
~60 cycles for Athlon64s
RAM is made to be accessed very often in relatively short bursts.
Until SSDs can get the latency down, they have no hope of replacing RAM.
If mass storage were as quick as RAM, you wouldn't dedicate part of it to be used as RAM.
Rather, you would manipulate the files directly from the mass storage device.
This would eliminate RAM all together, reducing overhead and potentially power consumption.
Unfortunately, no current mass storage device has the potential to do that.
I'm still waiting for MRAM to make its appearance.
It used to hold promise, but after waiting so long I lost interest and stopped keeping up with it.
Perhaps it can do what flash can not.
That is good information but I would like to have seen 3GB numbers using a 2GB and a 1GB SODIMM.
Well, if battery life goes up on a laptop that significantly would not power consumption on a desktop also improve? If so, this would be a noteworthy fact. I could easily see the extra ram paying for itself in energy savings not to mention helping the environment.
If you wan't maximum battery with 2 or 3GB just turn off the swap-file.
You could just turn off swap space. Then it wont use the harddrive, thus preserving battery life. I refuse to run vista, preferring Linux and xp in dual boot.
Feeding the OS endless amounts of ram is not a long term solution to an underlying performance issue. I can run Ubuntu linux with all the fancy compiz-fusion eye candy with just 512mb and it's smooth. Vista doesn't run smooth even with 1gb; it's a real dog. I understand why everyone is avoiding it like the plague, except of course those poor unfortunates who bought into the Direct X 10 marketing fallacy, and others who bought a new machine with it preinstalled (microsoft tax).
Just make sure that once you put in that 4GB's of RAM, that you TOTALLY disable the swap file on the hard drive. I've done that for my notebook, and it gets nearly 3 times the battery life that it did after putting in 4GB's of memory and before disabling the swap file totally.
Hi, Ive never taken a laptop completely apart before and was wondering how I would remove the keyboard to get to the second ram bay, any info and pics of the process u can give will be greatly appreciated, thx in advance
I just recently purchased the ocz 4gb pc2 5400 (2x2gb) for d630 with winxp. I know that it can only recognize 3.5gb but my computer crashes everyweekend i take it home with blue screen. It only happens when I travel back from abilene to dallas (3hr drive) but I keep it in a laptop bag. Can I really have damaged or unseated the memory or do i just have bad memory to begin with? The install was done by dell certified techs and noticed that dell 2gb was pc5300 and ocz's were 5400, does that make a difference? Dunno if its user error with not handling laptop correctly( which i do) or just bad memory. Problem does not happen during time spent at school.
I'm planning to upgrade my laptop's memory. Should I get two 1GB memory or one 2BG memory? Does it matter?
Thank you!
just go 4gb, its only $40-70 (2 x2gb)= if u get 1 2gb stick u can have 3gb by replacing one slot