Intel's Warning on Memory Voltage

One of the most interesting changes for us with the release of the i7/X58 platform is the advances that have been made with DDR3. DDR3 had an auspicious introduction over a year and half ago when the P35 chipset debuted. Intel then introduced the X38 chipset with a focus on DDR3 support although DDR2 continued to perform better on the platform. It was not until the Intel X48 and NVIDIA 790i chipset releases earlier this year that users recognized DDR3 could become a performance factor on the desktop.

However, in order to glean the absolute best performance from these chipsets, the user needed DDR3 that was capable of running higher than DDR3-1800 speeds. The ICs from Micron at the time required a healthy 1.9V or higher to reach those speeds and the coveted 2000MHz mark. Samsung introduced a new family of ICs last spring that were capable of running up to 2200MHz or higher on +2.0V. While typical desktop applications or games did not take advantage of these speeds and resulting memory bandwidth, they did make for top results in the synthetic benchmarks.

Pricing was another problem that prevented the growth of DDR3 into the main stream market. Not only was DDR3 expensive, the market was flooded with DDR2 memory that performed equally well on the desktop at over half the price. As with most new technologies, it is a chicken and egg scenario when it comes to mass market product acceptance.

Intel had originally planned on X38/X48 being DDR3 only, but the market was not ready for it. We still feel that way to some degree but Intel believes this is the time for DDR3 to become their memory technology of choice for the next few years. As such, the introduction of i7/X58 brings with it a requirement for DDR3 memory. This requirement comes with a couple of caveats, the primary one being that Intel is highly recommending, more like suggesting a visit from the Grim Reaper is coming soon, that memory voltage does not exceed 1.65V on a long term basis or your new i7 might not work one day.

The majority of current DDR3-1066/1333 modules adhere to the base 1.5V JEDEC spec along with not needing more than 1.65V when overclocking, although overclocks amount to a couple hundred MHz increase at best with these products. The higher end DDR3 that has been on the market since last winter typically requires 1.8V or so to run above DDR3-1600. In fact, most of the current DDR3-1800+ memory usually requires 1.9V or higher. In some cases, depending on the SPD, it has difficulty even booting at 1.5V.

By coincidence or not, newer DDR3 ICs coming to market now from Qimonda, Samsung, and Elpida are able to operate from DDR3-1066 up to DDR3-1800 on 1.5V to 1.65V depending on timings and module size. In fact, we have experience with the new Samsung and Qimonda ICs (both 3GB and 6GB kits) operating at DDR3-1866 (9-9-8-20) up to DDR3-2000 (10-9-9-24) on 1.65V~1.75V with the ASUS Rampage II Extreme board. The good news is that these modules are starting to show up at the e-tailors with price points below previous DDR3 products.

This last week has been a busy one in the labs as we have started to receive a variety of memory modules from Kingston, OCZ, Patriot, GSkill, and Corsair for our upcoming DDR3 Shootout and Memory Guide for i7. The products range from the $109 3GB DDR3-1333 (9-9-9-24) kit from GSkill to the Corsair/OCZ 6GB DDR3-1600 (9-9-9-24) kits, and finally our DDR3-2000 (9-9-9-24) 1.65V kit from Kingston.

Our initial opinion at this time is that dual or tri-channel DDR3-1333 running at 8-8-8-20 timings will satisfy about 80% of the users in the market. In fact, DDR3-1066 at 7-7-7-18 might be the better solution for most applications right now considering the latency improvements over CAS8 or CAS9 DDR3-1333. Of course, running DDR3-1333 at CAS7 would be ideal from a price and performance viewpoint.

For the more performance oriented crowd, we have found the sweet spot for performance and keeping money in your wallet, to be tri-channel DDR3-1600 running at 8-8-8-20, something most of the new DDR3-1600 6GB kits will do easily on 1.6V or less. Of course, the benchmarking enthusiast will still want DDR3-1866 or higher on this platform. Something that is attainable now with voltages in the 1.65V~1.75V range depending on final speeds, board design, and loads as all three i7 processors are memory multiplier unlocked.

Getting back to that 1.65V warning, Intel is quite serious about this voltage level and is ensuring the board manufacturers remind the users in a variety of ways ranging from statements in the user manuals to various BIOS warnings when changing VDimm above 1.65V. We have been running exhaustive tests at various voltages and firmly believe that if VCore, QPI/IMC Voltage, and VDimm are properly aligned, that running VDimm up to 1.80V should be acceptable with proper cooling and non 24/7 operation. Of course that is not a promise, but we will have additional results shortly.

In the meantime, Intel also recommends not taking QPI/IMC (uncore/VTT) voltages above 1.3V. In fact, we think this setting is just as dangerous as or more so than high VDimm to the processor’s long term health. However, this setting is also one that greatly improves memory clocking and bclk levels along with a proper dose of IOH voltage. Just how far you can take QPI/IMC (VTT) voltage is something we are working on (1.475V is working well for us), just be aware that it is a delicate balance between this setting and VDimm to get the most out your memory. In most of our tests at this point on the 920, we usually bump QPI/IMC (VTT) voltage up to get additional memory/core clocks while maintaining the memory voltage around 1.65V.

What about the Impact of DDR3 Speeds? Thread It Like Its Hot
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  • Kaleid - Monday, November 3, 2008 - link

    http://www.guru3d.com/news/intel-core-i7-multigpu-...">http://www.guru3d.com/news/intel-core-i...and-cros... Reply
  • bill3 - Monday, November 3, 2008 - link

    Umm, seems the guru3d gains are probably explained by them using a dual core core2dou versus quad core i7...Quad core's run multi-gpu quiet a bit better I believe.

    Reply
  • tynopik - Monday, November 3, 2008 - link

    what about those multi-threading tests you used to run with 20 tabs open in firefox while running av scan while compressing some files while converting something else while etc etc?

    this might be more important for daily performance than the standard desktop benchmarks
    Reply
  • D3SI - Monday, November 3, 2008 - link


    So the low end i7s are OC'able?

    what the hell is toms hardware talking about lol
    Reply
  • conquerist - Monday, November 3, 2008 - link

    Concerning x264, Nehalem-specific improvements are coming as soon as the developers are free from their NDA.
    See http://x264dev.multimedia.cx/?p=40">http://x264dev.multimedia.cx/?p=40.
    Reply
  • Spectator - Monday, November 3, 2008 - link

    can they do some CUDA optimizations?. im guessing that video hardware has more processors than quad core intel :P

    If all this i7 is new news and does stuff xx faster with 4 core's. how does 100+ core video hardware compare?.

    Yes im messing but giant Intel want $1k for best i7 cpu. when likes of nvid make bigger transistor count silicon using a lesser process and others manufacture rest of vid card for $400-500 ?

    Where is the Value for money in that. Chukkle.
    Reply
  • gramboh - Monday, November 3, 2008 - link

    The x264 team has specifically said they will not be working on CUDA development as it is too time intensive to basically start over from scratch in a more complex development environment. Reply
  • npp - Monday, November 3, 2008 - link

    CUDA Optimizations? I bet you don't understand completely what you're talking about. You can't just optimize a piece of software for CUDA, you MUST write it from scratch for CUDA. That's the reason why you don't see too much software for nVidia GPUs, even though the CUDA concept was introduced at least two years ago. You have the BadaBOOM stuff, but it's far for mature, and the reason is that writing a sensible application for CUDA isn't exactly an easy task. Take your time to look at how it works and you'll understand why.

    You can't compare the 100+ cores of your typical GPU with a quad core directly, they are fundamentaly different in nature, with your GPU "cores" being rather limited in functionality. GPGPU is a nice hype, but you simply can't offload everything on a GPU.

    As a side note, top-notch hardware always carries price premium, and Intel has had this tradition with high-end CPUs for quite a while now. There are plenty of people who need absolutely the fastest harware around and won't hesitate paying it.
    Reply
  • Spectator - Monday, November 3, 2008 - link

    Some of us want more info.

    A) How does the integrated Thermal sensor work with -50+c temps.

    B) Can you Circumvent the 130W max load sensor

    C) what are all those connection points on the top of the processor for?.

    lol. Where do i put the 2B pencil to. to join that sht up so i dont have to worry about multiply settings or temp sensors or wattage sensors.

    Hey dont shoot the messenger. but those top side chip contacts seem very curious and obviously must serve a purpose :P

    Reply
  • Spectator - Monday, November 3, 2008 - link

    Wait NO. i have thought about it..

    The contacts on top side could be for programming the chips default settings.

    You know it makes sence.Perhaps its adjustable sram style, rather than burning connections.

    yes some technical peeps can look at that. but still I want the fame for suggesting it first. lmao.

    Have fun. but that does seem logical to build in some scope for alteration. alot easier to manufacture 1 solid item then mod your stock to suit market when you feel its neccessary.

    Spectator.
    Reply

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