Articles: Memory

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Again on Voltages

Before we move on to the specific memory kit in question, that is going to be the main hero of our today’s review, we would like to talk once again about the real need for choosing low-voltage memory. Because of this particular factor it is impossible to use in LGA1366 platforms most overclocker DDR3 solutions available by users and in retail channels. And since users more often start to doubt the need for the low recommended maximum voltage, we simply couldn’t leave out this important topic.

First of all, I have to say that the 1.65V number is not just some number. Although the standard voltage for DDR3 SDRAM is 1.5V, Intel engineers believe that the slightly increased maximum voltage is safe for LGA1366 systems. Mainboard makers stand by them warning about possible processor damage if VDIMM ever exceeds 1.65V. And these warnings and concerns emerge for a reason. The thing is that Core i7 processors use VDIMM to power the integrated memory controller, too. That is exactly why it is so dangerous to increase this parameter excessively.

At the same time, there is an opinion that when the voltage of the CPU Uncore part is raised past 1.1V, the maximum VDIMM settings may be increased, too. It is partially true, because processor logic is more sensitive not to the absolute voltages but to the ratios between the signal levels. Therefore, it is considered possible to increase the memory voltage past 1.65V only if Uncore processor voltage is increased at the same time. Note that the ratio between the memory and Uncore voltages should not exceed 1.5: only in this case the consolidated voltage increase may be considered relatively safe. At least our practical experience in this matter suggests that you will be able to prolong the life of your CPU if you follow this recommendation carefully.

However, there is another danger here. If you increase Uncore and memory voltages, the heat dissipation of the CPU part containing L3 cache and the memory controller will increase rapidly. There is no way to control this process, because Intel engineers didn’t integrate any thermal or alarm diodes in this part of their CPU die: all diodes inside Core i7 processors are exclusively inside the actual computational cores. In other words, extreme increase of the VDIMM and VUncore may lead to systematic uncontrollable heating of the integrated memory controller, which may eventually lead to very sad consequences. Core i7 may degrade and with the time even die without proper cooling.

Therefore, we support Intel’s recommendations and strongly suggest that you should equip your LGA1366 systems only with those memory modules that do not require increasing their voltage over 1.65V.

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