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Skylake's IMC Supports Only DDR3L

When Skylake was released, Intel announced the move to the new DDR4 standard while maintaining limited support for DDR3. Initially, evidence indicated that Skylake could support only DDR3L, but since that time, motherboard OEMs have listed support for non-DDR3L RAM, which raised obvious questions. After speaking with Intel about the issue, we finally know the truth about what RAM Intel's integrated memory controller (IMC) can support.

Skylake's IMC officially supports only DDR3L with a voltage of 1.35, and it officially supports DDR4 at 1.2 V. This might seem a little counter-intuitive to some users, as the entire reason for continuing DDR3 support is to make it cheaper and easier for customers to upgrade to the new Skylake platform, but these voltages are likely used to avoid damaging the IMC. Although it would be nice to use any DDR3 from 1.35 V - 1.65 V, running at these higher voltages could burn out the IMC and kill the processor over time.

If this is the case, though, then why do OEMs such as Gigabyte support DDR3 at 1.5 V on some of their motherboards? And why do others such as Asus and ASRock support DDR3 at 1.65 V? RAM running at these voltages might be capable of operating on the motherboard without causing damage to the board itself, but again, over time it will likely damage the CPU. So if you don't have DDR3L on hand, you are probably better off to go ahead and spring for the more expensive DDR4.

Another interesting point that we learned from Intel about the IMC is that it only supports clock speeds up to 4,133 MHz. Although DDR4 is still relatively new, and most RAM kits currently run between 2,133 and 3,000 MHz, some RAM kits are already reaching beyond 4,233 MHz.

RAM kits running at clock speeds above 4,133 MHz will likely encounter more errors than other DDR4, and it is probably best to limit yourself to memory running below this clock speed for the time being. DDR4 at higher clock speeds will become more useful in the future as Intel refines its IMC to support faster RAM, but that isn't likely to happen until a Skylake refresh or the release of Cannonlake.

Long story short, if you are looking to buy a Skylake platform, make sure you double check the RAM you are buying to avoid having problems down the line. Even if it works initially on your system, there is no guarantee that under stress the IMC won't break down and knock your system out of commission.

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  • rgd1101
    Can you contact any motherboard manufacturer for comment?
    From pcpartpicker look like DDR4 3000MHz and greater are 1.35v
    Reply
  • Sakkura
    What this article fails to mention is that most kits of DDR3 rated at 1.5V can still run at 1.35V. Just at lower clocks.
    Reply
  • IInuyasha74
    What this article fails to mention is that most kits of DDR3 rated at 1.5V can still run at 1.35V. Just at lower clocks.

    This article wasn't about how to fix RAM to work on your system, it was to discuss what Intel officially supports. Not everyone will know how to lower the voltage and clock settings on their RAM, and not all RAM will operate at lower voltages even if you lower the clock speed. That is something users will need to test for themselves on a case by case basis.
    Reply
  • synphul
    Glad they cleared this up. Many initial reports I'd read about it indicated exactly this, that skylake's memory controller was capable of ddr4 or ddr3L (low power ddr3, not standard ddr3). When some dual memory type boards or ddr3 enabled z170 boards came out they were claiming ddr3 native support as if someone could just move their ddr3 ram to the new board and have it work just fine. It didn't make sense considering the voltage differences.

    Agreed, the article isn't about fiddling with everything to get it to work and underclocking ram (having it perform worse) or anything else. People need to be made aware of the differences in the chips and the differences in the new memory standards. Half the reason to upgrade to the new platform is to upgrade, not piece it together and macgyver it with duct tape to force it to work or it defeats the purpose.
    Reply
  • IInuyasha74
    16697163 said:
    Can you contact any motherboard manufacturer for comment?
    From pcpartpicker look like DDR4 3000MHz and greater are 1.35v

    Those might work fine too, but it is hard to say. Motherboard manufacturers have very little to do with RAM support really, as the CPU's IMC controls virtually all aspects of the RAM. Intel probably had its reasons why it didn't add support for DDR4 at 1.35 V, but that RAM may work fine still. Similar with DDR3 on Sandy Bridge and Ivy Bridge, only 1.5 V was supported. Sandy Bridge only supported up to 1333 MHz, and Ivy Bridge only supported up to 1600 MHz, but other RAM kits that feature higher voltages and clock speeds have been used countless times.

    Not being supported by Intel doesn't mean that it necessarily won't work, but that it is either untested or unsupported for some reason, and may cause problems.
    Reply
  • Sakkura
    16699802 said:
    Agreed, the article isn't about fiddling with everything to get it to work and underclocking ram (having it perform worse) or anything else. People need to be made aware of the differences in the chips and the differences in the new memory standards. Half the reason to upgrade to the new platform is to upgrade, not piece it together and macgyver it with duct tape to force it to work or it defeats the purpose.

    The problem is that the article says people can't use their existing DDR3 memory with Skylake, which is going to be wrong in most cases. Most DDR3 can run at 1.35V just fine.
    Reply
  • IInuyasha74
    16700921 said:
    16699802 said:
    Agreed, the article isn't about fiddling with everything to get it to work and underclocking ram (having it perform worse) or anything else. People need to be made aware of the differences in the chips and the differences in the new memory standards. Half the reason to upgrade to the new platform is to upgrade, not piece it together and macgyver it with duct tape to force it to work or it defeats the purpose.

    The problem is that the article says people can't use their existing DDR3 memory with Skylake, which is going to be wrong in most cases. Most DDR3 can run at 1.35V just fine.

    But without lowering the DDR3 to 1.35 V, it will likely cause damage over time. Again, this article was to discuss the official RAM support of Intel's IMC. This article is not to discuss ways to get unsupported RAM to run within these limitations.
    Reply
  • Sakkura
    16702337 said:
    But without lowering the DDR3 to 1.35 V, it will likely cause damage over time. Again, this article was to discuss the official RAM support of Intel's IMC. This article is not to discuss ways to get unsupported RAM to run within these limitations.

    Lowering the voltage that way is possible with most DDR3. Thus this statement in the article is misleading:

    So if you don't have DDR3L on hand, you are probably better off to go ahead and spring for the more expensive DDR4.

    You're advising people to spend money on DDR4 when they can most likely continue to use their DDR3 memory. That's simply bad advice.
    Reply
  • rgd1101
    Not a bad advise, telling people what they should do, not they have to.
    Reply
  • dextermat
    Why beat a dead horse, ddr4 is out on the market. Hence when their is no competition the market slows down to milk as much money as possible. Too bad.
    Reply