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Tom's Ultimate RAM Speed Tests

Is Fast Memory Really Worth It?

Memory vendors have become excellent at marketing their latest high-end products: DDR3-2000 speeds are currently considered state of the art for enthusiast Intel platforms based on Intel’s P35, X38, X48 chipsets or the new Nvidia 7 series. But how much sense do these products really make? While mainstream DDR2 memory has reached almost ridiculously low price levels - you can get two 2 GB DDR2-800 DIMMs for less than $80 - DDR3 memory at 1600 speed or faster easily costs five times as much, without delivering even double the performance. In fact, for the vast majority of users, the difference between mainstream and high-end memory turns out to be extremely small.

The importance of Random Access Memory (RAM) has changed a lot over time. There were noticeable performance differences between CL2 and CL3 timings back at the turn of the millennium, when first generation SDRAM at PC100 or PC133 speeds were popular. But now, the performance delta between quick and very relaxed timings is almost negligible in using fast DDR2- or DDR3-SDRAM. Although memory latencies seem to have increased from one memory generation to the next (CL2/3 with DDR1, CL3-5 with DDR2, CL5 and up with DDR3), the latencies haven’t changed much, as the clock speeds have doubled with each generation change. The effective latencies hence remained very much the same, while throughput has increased considerably. (Compare Prices on DDR)

Enthusiast memory does have another justification that is only indirectly based on performance: overclockers need maximum flexibility from components when they want to squeeze out maximum performance from their systems. Increasing the system speed is often the only way to increase the CPU clock, which will automatically accelerate the memory as well, as its clock speed directly derives from the system clock speed. Since you don’t want to be performance-restrained by limiting memory speed, fast memory may be necessary to achieve maximum system performance. This scenario is only valid for hardcore overclockers, however, as the benefit of fast memory over slower has become very small if the other components and parameters remain unchanged.

We wanted to know how important RAM speed and timings really are. To test this, we assembled a Socket 775 system, which we operated using two different processors: a brand new 3.16 GHz Core 2 Duo E8500 based on the 45 nm Core 2 Duo Wolfdale core with 6 MB L2 cache; and a 3.73 GHz Pentium 4 Extreme Edition single core processor. We decided to include the old single core Netburst P4 processor since it offers a smaller and less efficient cache memory than the Core 2 Duo. Both processors were benchmarked at DDR2-667, DDR2-800 and DDR2-1066 speeds as well as DDR3-1066 and DDR3-1333, each time using slow and fast timings. The P4, however, could not be benchmarked at DDR3-1333 speed, as it would have required FSB1333.

  • digibri
    The article mentions a couple of times that you need a 64 bit operating system to utilize 4 GB or RAM because 32 bit (XP for instance) can only access 3 GB of memory.

    1) Is it true that 32bit XP can only access 3GB? I thought it was 3.5GB...

    2) If I build a system and load it with 4GB of memory, will 32bit XP work well enough (only accessing it's 3GB or 3.5GB maximum) or will it have difficulty running properly? Meaning, is it preferable or necessary to build a 32bit XP box with only 3GB exactly?

    Great article, thanks.

    B.
    Reply
  • digibri
    The article mentions a couple of times that you need a 64 bit operating system to utilize 4 GB or RAM because 32 bit (XP for instance) can only access 3 GB of memory.

    1) Is it true that 32bit XP can only access 3GB? I thought it was 3.5GB...

    2) If I build a system and load it with 4GB of memory, will 32bit XP work well enough (only accessing it's 3GB or 3.5GB maximum) or will it have difficulty running properly? Meaning, is it preferable or necessary to build a 32bit XP box with only 3GB exactly?

    Great article, thanks.

    B.
    Reply
  • imatt
    Yes XP32 can access 3GB, but it subtracts the amount of RAM on your video card from that. So if you have 512MB or RAM on your video card, XP32 would only see 2.5GB of system RAM. I went through this last week when I upgraded to 4GB RAM, so I switched to Vista64. Gaming rig. No regrets.
    Reply
  • digibri
    How does XP64 do these days? Is there better driver support?
    Reply
  • creepster
    "More memory, meaning 4 GB, requires a 64-bit operating system..."

    Except it doesn't. 32bit Linux can use in excess of 4GB of memory, though not on all chipsets. I was looking at this issue only yesterday. I was unable to see 4GB with a motherboard using an Intel 945 chipset but on with an Intel 965 chipset I was able to see all 4GB just fine using the bigsmp kernel.
    Reply
  • sailer
    9456991 said:
    How does XP64 do these days? Is there better driver support?

    I find that XP64 does quite well. I've had it on one of my computers for a year now and have had no driver troubles. That's one thing I think Vista 64 has been for, getting the hardware companies to finally make 64 bit drivers. Also, in comparing my machine with XP64 and the one with Vista 64, the XP64 is much easier to use. Of course, the XP64 does not support gaming with DX10. I'll be building a new office machine during the next month and after using Vista 64 the past few weeks on my gaming machine, I'll install XP64 on the office machine.

    As to the article on the ram, I didn't see it answer anything new, only confirm what was already thought. One poorly written part was page 4, "How ram sensitive are different CPUs?" The following paragraph didn't seem to address the opening line at all. Even in the conclusion of the article, there was not much said to answer the question, just an allusion that memory type was was of small relevance to either of the CPUs.
    Reply
  • philbob10
    The actual amount 32-bit Windows can see without Extended Memory Addressing turned on is 3.3GB. This is a result of the OS using the addresses past the 3.3 boundary for addressing hardware, etc. Having 4GB in your system will not affect your performance.

    Linux can address more than 3.3GB and beyond with the 32-bit kernel using the same means the Windows Server variants can, by using Extended Memory Addressing, and it's support is dependent on the memory controller and BIOS, as well as the OS.
    Reply
  • hawk4031
    Well according to Microsoft's website, Vista 32-bit can now fully use 4gb of RAM without subtracting off the total memory in your computer.

    Here is the article:

    http://technet2.microsoft.com/WindowsVista/en/library/005f921e-f706-401e-abb5-eec42ea0a03e1033.mspx?mfr=true

    Scroll down to the "General Improvements and Enhancements" section. It is the second bullet point. Just thought I would point this out seeing as there is a RAM limit with 32-bit XP.
    Reply
  • drewd
    Something seems wrong with the data on page 3. Both DDR2 and DDR3 have a single clock that runs at the same speed at the I/O bus - for example, a DDR2-800 module has a 400MHz clock. What the table calls an "I/O clock" sounds more like the data strobes, which are not clocks. They also run at the same speed as the I/O bus, but are not free-running, like the clock. They only run when there are I/O operations. It looks like somebody confused CKE or CS with the clock. Either that, or there's a fundamental misunderstanding about what the "8 bit prefetch" is.
    Reply
  • 32bit operating systems can support a maximum of 4gb of ram. but you must subtract video ram and cpu cache from this total.
    Reply