Tom's Ultimate RAM Speed Tests

RAM Choices

The memory market is in the process of transitioning from DDR2 memory to the more efficient and higher density DDR3 technology; this process will be underway until the end of the year. DDR2 is available at 800 and 1066 speeds, while DDR3 reaches from 800 to 1333. Faster products are still enthusiast-class premium products, as no platform offers official support for 1600+ speeds yet.

Both technologies are based on the double data rate principle, which means that they transfer data twice per clock cycle: during the rising and falling edge of the clock signal. Each new DDR memory generation is based on smaller transistors, decreased voltage levels and higher memory density. While the internal clock speeds don’t change, the clock speed at the interface (I/O buffer) has been increasing due to an increasing level of what is called prefetch. DDR3-1600 memory works on a physical memory clock of 200 MHz, but at a prefetch of eight. The interface runs at 800 MHz, but thanks to double data rate mode, this equals a 1600 MHz frequency. DDR2-800 also runs at a 200 MHz base clock, but with a prefetch of four.

As already mentioned, performance shouldn’t be the primary reason to switch from one memory generation to the next. Memory densities, however, are more interesting. While 1 GB DIMMs (1 Gbit ICs) can be considered mainstream in the DDR2 market, DDR3 memory will be the dominant technology once 2 GB DDR3 DIMMs become affordable, and once AMD has switched to it as well, later this year.

Which Memory Should You Buy?

However, the best deals on memory can clearly be found in the DDR2 mainstream. If budget is an issue, any 2x 1 GB DDR2 brand memory kit at DDR2-800 speed will do the job perfectly well. As you will see in the benchmark section, only significantly faster (and significantly more expensive) memory can deliver a tiny performance advantage. We don’t even recommend going for DDR3 motherboards, unless you’re purchasing something in the high-end. When you’re looking at several hundred dollars for a motherboard, and similar price points for a Core 2 Quad processor and decent system components, it is acceptable to spend some more on the memory. For anyone with a limited budget, though, it’s not.

2 GB memory kits offering two DDR2-800 modules start at approximately £40, which can be considered a bargain given that 2 GB of main memory is enough to run all sorts of mainstream applications and games. More memory, meaning 4 GB, requires a 64-bit operating system, because Windows XP and Windows Vista will only be able to handle 3 GB RAM when the 32-bit versions are used. Although the 64-bit versions are equally reliable, almost equally fast, and driver support has improved a lot, be sure you double check if your devices and applications will work in a 64-bit environment.

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  • "It’s worth noting that DDR2 memory is amazingly affordable at its current pricing point. 4 GB kits look especially appealing, but remember that you’ll need a 64-bit operating system to take advantage of all of it."

    That's not strictly true. Windows Vista SP1 can now recognise 4GB of RAM on a 32 bit system.
  • As always, a very interesting article. I had heard that Vista 32 bit SP1 was going to have 4Gb memory support. Is this correct?
  • And before you say "Vista SP1 only recognises the RAM but does not address it." you could use Physical Address Extensions to utilise the extra RAM.
  • What I found interesting is that on the C2D, the 667 MHz 3-3-3-8 pretty consistently outperformed the 800 MHz 3-3-3-8. Apperantly, the 1:1 divider is so much more efficient than the 5:6 divider, that the clock speed is a smaller factor.
    I have a C2D 8400 running with DDR2-800, I'm gonna try if running it at 667 MHz will improve performance. Didn't expect that.
  • 32bit OS's cant use 4Gb of RAM its a limitation of the x86 architecture. 32Bit OS can only address up2 4Gb if u have a GFX card with 512Mb theres half a gig gone there and then so windows could only use the remaining 3.5Gb for RAM. Now jus imgaine 2x 8800GTX's in Sli 768Mb Each!!
  • Does anyone read previous posts?
    I'm sure graphics cards with any amount of RAM use it independant to whatever Windows has so I'm pretty sure what Matt26LFC said is not quite correct.
  • Fidens1 - there is no difference between Vista and Vista SP1 in their ability to address 4 Gb of RAM.

    The only difference is that under SP1, Vista displays the amount of INSTALLED RAM rather than the amount available to Windows - see the information in the Microsoft article about the Vista SP1 changes, here:

    It's the second bullet point under the "General Improvements and Enhancements" section.

    As for Physical Address Extension, that's something quite different, and not unique to Vista SP1 or even to Vista - Windows XP can do that.
  • Matt26LFC is correct. Although the RAM on the graphics card is independant, it still forms part of the total addressable space. Running a 64bit OS resolves the addressable memory barrier even if it does introduce other side issues...
  • Yes, but with SP1 you can now "SEE" the amount of RAM installed (up to 4GB) as well as use it with Physical Address Extensions. So really, going back to the article, you can use 4GB and see it in a 32 bit system.

    Using Physical Address Extension, surely this could offset the RAM on the graphics card?
  • Even with PAE, addressable space remains at 4GB in a 32 bit OS. PAE provides a mechanism where by memory beyond 4GB can be used by applications capable of making use of it, for example, SQL server. It does this by creating multiple processes.
  • PAE is patchy at best when used not thing you norm use (and vista does not support it officialy and will more then likey result in an BSOD alot)

    Vista 32 and vista 32 SP1 Does Not support more ram then each other, Vista NOW reports the Amount Of Installed RAM Not what is usable what very poor way that microsoft have done this as now thay are hideing the fact that laptops with 256mb shared ram does not show it been used any more, thay should of shown both ways total installed total usable (and an help box to explane why usable is lower then installed)

    Plase task manager (press Ctrl-Shit-Esc will open it as well) and click on performace and you see how much ram is usable there under Physical > total {4gb = 4000 ish}

    with an 32bit OS with 4gb depeding on more then 1 video card is in use or motherbaord as well it be anywhere between 3.5gb {3500 ish} all the way down to 2gb {2000 ish} of useable ram on Any 32bit os
  • Cant believe the way microsoft have handled this, trying to make people think they can now use 4Gb+ i agree with u leexgx that should show both values and throw in a help box to explain.
  • Any chance of you doing the same or similar tests on an AMD Phenom system?
  • Power consumption?
  • Is Aeneon's semi transparent (x layers PCB) with aeneon chips much slower than decent looking Buffalo sticks and both of them much slower than OCZ sticks. All ddr2 800, 5-5-5-12?

    Anyone compared this low cost sticks with high cost sticks? Any differences in %?
  • So if you already have 2 gig installed, have 1 gig of graphics RAM, what size swop file can you use? Is it addressed differently?
  • I Have an Asus P5N T Delux Motherboard with an intel Qx9650 CPU a 750GB Seagate Barracuda with 32Mb Cache and also have 2xGeForce 880GTX Graphics cards with 768MB DDR3 memory and 8GB of PC6400 800 Geil Black Dragon Ram can anyone tell me if its possible to run faster memory with my setup or would it not be cost effective to go for faster memory? I have Vista Ultimate 64Bit OS which recognises my 8GB of Memory and I have 6280MB Free. What memory would be best for this setup and where can I get it from? my systems Motherboard has a 1333FSB I think sorry to be so vague but I dont know a lot about memory or motherboards.