Z370 Extreme4 XMP bug

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 parsec wrote:

These posts seem to confirm the issue. I say "seem" only because it is unusual for an issue to apply 100% of the time when there are hardware variables involved. The variables here are different models of memory, with differing OC speeds applied by the XMP profile.

Enabling the XMP profile causes an automatic increase in the VCCIO and VCCSA voltages. That is not caused by the XMP profile itself, but the code in the UEFI. That is a standard adjustment when over clocking memory, it normally enhances stability.

The interesting thing here is, all three users posting about this issue are using 3200 speed memory. My guess is the voltage values used for VCCIO and VCCSA when the XMP profile is enabled is simply one voltage value, regardless of the memory OC speed. 

A memory OC of 3200 is not a very high memory over clock relative to Intel Z370 and Z270 boards and the Kaby Lake and Coffee Lake processor's memory controllers. Memory over clocks for Z370 and some Z270 systems of over 4000 are possible. The high VCCIO and VCCSA voltages are more appropriate for use with memory over clocks over ~3600.

The purpose of the high VCCIO and VCCSA voltages applied when the XMP profile is enabled is to insure (as much as possible) a memory OC will POST successfully. As we see with CPU over clocks, more VCore is needed, but too much is unnecessary and we reduce it to an appropriate value.

The problem is all users are not aware of the need to configure the VCCIO and VCCSA voltages with memory over clocks. The memory OC potential of the memory controller is also a factor. The compromised solution is to set them on the high side.

VCCIO and VCCSA voltages also? tend to be "sweet spot" type voltages, the optimum values need to be dialed in for the memory being used, and the OC speed. Increasing them worked with memory over clocks, but too much was not known to cause stability issues, at least with Z270 systems.

My ASRock Z270 board's UEFI also set the VCCIO and VCCSA voltages higher
 than was needed with my G.SKILL 3600 memory. But I did not experience 
any of the freezing issues described here. talos reported the same experience with his Z270 system. I am surprised that reducing 
those voltages caused the freezing to stop, given past experience. I'm glad that it did. It seems things have changed with the memory controllers in Coffee Lake processors.

FYI, you can check the actual applied VCCIO and VCCSA voltages in the H/W Monitoring screen in the UEFI, and in Windows with programs such as HWiNFO64. My point is the actual/resulting voltage tends to be a bit more than the value entered for either option, according to the readings. You might want to select a slightly lower value for the option, to achieve a perfect result for your memory.

I think strange that when I put my T-Force Vulcan ( 8GB DDR4 2400 - TLRED48G2400HC1601) and enter the Bios, it shows the option to load XMP Setting and the pc boots normally.
But when I insert the G.Skill TridentZ RAM this option is not available.
I tried G.Skill RAM in A1 and B1 slots, and then in A2 and B2 slots and edited the voltage settings of VCCIO to 1.1V and VCCSA to 1.15V.