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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  • npp - Tuesday, November 4, 2008 - link

    Well, the funny thing is THG got it all messed up, again - they posted a large "CRIPPLED OVERCKLOCKING" article yesterday, and today I saw a kind of apology from them - they seem to have overlooked a simple BIOS switch that prevents the load through the CPU from rising above 100A. Having a month to prepare the launch article, they didn't even bother to tweak the BIOS a bit. That's why I'm not taking their articles seriously, not because they are biased towards Intel ot AMD - they are simply not up to the standars (especially those here @anandtech). Reply
  • gvaley - Tuesday, November 4, 2008 - link

    Now give us those 64-bit benchmarks. We already knew that Core i7 will be faster than Core 2, we even knew how much faster.
    Now, it was expected that 64-bit performance will be better on Core i7 that on Core 2. Is that true? Draw a parallel between the following:

    Performance jump from 32- to 64-bit on Core 2
    vs.
    Performance jump from 32- to 64-bit on Core i7
    vs.
    Performance jump from 32- to 64-bit on Phenom
    Reply
  • badboy4dee - Tuesday, November 4, 2008 - link

    and what's those numbers on the charts there? Are they frames per second? high is better then if thats what they are. Charts need more detail or explanation to them dude!

    TSM
    Reply
  • MarchTheMonth - Tuesday, November 4, 2008 - link

    I don't believe I saw this anywhere else, but the spots for the cooler on the Mobo, they the same as like the LGA 775, i.e. can we use (non-Intel) coolers that exist now for the new socket? Reply
  • marc1000 - Tuesday, November 4, 2008 - link

    no, the new socket is different. the holes are 80mm far from each other, on socket 775 it was 72mm away. Reply
  • Agitated - Tuesday, November 4, 2008 - link

    Any info on whether these parts provide an improvement on virtualized workloads or maybe what the various vm companies have planned for optimizing their current software for nehalem? Reply
  • yyrkoon - Tuesday, November 4, 2008 - link

    Either I am not reading things correctly, or the 130W TDP does not look promising for the end user such as myself that requires/wants a low powered high performance CPU.

    The future in my book is using less power, not more, and Intel does not right now seem to be going in this direction. To top things off, the performance increase does not seem to be enough to justify this power increase.

    Being completely off grid(100% solar / wind power), there seem to be very few options . . . I would like to see this change. Right now as it stands, sticking with the older architecture seems to make more sense.
    Reply
  • 3DoubleD - Tuesday, November 4, 2008 - link

    130W TDP isn't much worse for previous generations of quad core processors which were ~100W TDP. Also, TDP isn't a measure of power usage, but of the required thermal dissipation of a system to maintain an operating temperature below an set value (eg. Tjmax). So if Tjmax is lower for i7 processors than it is for past quad cores, it may use the same amount of power, but have a higher TDP requirement. The article indicates that power draw has increased, but usually with a large increase in performance. Page 9 of the article has determined that this chip has a greater performance/watt than its predecessors by a significant margin.

    If you are looking for something that is extremely low power, you shouldn't be looking at a quad core processor. Go buy a laptop (or an EeePC-type laptop with an Atom processor). Intel has kept true to its promise of 2% performance increase for every 1% power increase (eg. a higher performance per watt value).

    Also, you would probably save more power overall if you just hibernate your computer when you aren't using it.
    Reply
  • Comdrpopnfresh - Monday, November 3, 2008 - link

    Do differing cores have access to another's L2? Is it directly, through QPI, or through L3?
    Also, is the L2 inclusive in the L3; does the L3 contain the L2 data?
    Reply
  • xipo - Monday, November 3, 2008 - link

    I know games are not the strong area of nehalem, but there are 2 games i'd like to see tested. Unreal T. 3 and Half Life 2 E2.. just to know how does nehalem handles those 2 engines ;D Reply

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