My intention was to place four Kingston DDR3 ValueRAM 4 GB 1.5V Modules at 1333MHz/CL9 on my new H170 (Skylake) motherboard, which officially supports memory running up to 1.65V. However, apparently using voltages higher than 1.35V can damage the integrated memory controller of Skylake CPU's. I'm debating on whether to

  1. return my motherboard in exchange for a DDR4 motherboard (and also buy DDR4 memory),
  2. reduce the DDR3 voltage from 1.5V to 1.35V without changing the frequency,
  3. or to just take the gamble and run the DDR3 DIMM's at 1.5V (which I feel very reluctant about).

And that would mean the following:

  1. This option would probably be the easiest, but because of my budget I'm reluctant to buy 16GB of RAM all over again.

  2. Since 1333MHz is the frequency of the RAM and the minimum supported frequency by the board, I was wondering if I could reduce the voltage from 1.5V to 1.35V without reducing the frequency. How stable is a 1333MHz DDR3 voltage reduction from 1.5V to 1.35V without underclocking?

  3. Is it likely that the Asus motherboard supplies additional voltage to the DIMM's (on top of the voltage supplied by the IMC)? EDIT: I just called Asus and they said no.

Which of the three options do you recommend and why?

  • You should be able to undervoltage the memory modules but at any point the settings are reset, you risk, the chances of the voltages changing. – Ramhound Oct 5 '15 at 15:58
  • You should ask Asus. C) may be possible, but it's them who are qualifying an unsupported configuration. Most RAM will work while undervolted fine, though quite how far depends on the chip(s). Just like the "overclocking = damage" and "heat = damage" myths that are constantly repeated, I'm yet to see any confirmed occurrence of damage being caused by running higher voltage through the Skylake IMC. – qasdfdsaq Oct 5 '15 at 16:04
  • According to the article, the IMC damage would likely take a while. Because Skylake hasn't been out that long, it could explain the lack of relevant reports thus far. – Wuschelbeutel Kartoffelhuhn Oct 5 '15 at 16:09

Although several sources say that it's dangerous to use higher voltages than Intel officially supports, there are also several anecdotal reports of users who have successfully run such systems for years (during the Nahalem days, a lot of people used 1.65V RAM vs. the Intel IMC supported 1.5V). The DDR3 RAM can likely be undervolted to 1.35V.
Another option is to insure the CPU for accidental damage (~$55 for three years). However, it is likely cheaper to sell the existing DDR3 RAM and then buy a DDR4 board with the corresponding DDR4 DIMMs. Whether the additional ~$50 (+mobo return hassle +DDR3 sell hassle) are worth the <6% performance gain of DDR4-2133 over DDR3-1333 and the peace of mind of not violating the official threshold (if the undervolting isn't successful/stable - i.e., the pessimistic outlook), is a question that depends on the difference in the failure rate, which isn't known, but likely < [opp_cost_DDR4]/[CPU_cost] = $50/$330 = 15% over a typical expected lifecycle of 5 years.

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