XMP isn't quite ideal

[voodoodrul]

Howdy folks. When I enable XMP on this Asus Maximus VII Impact board, 4790k, and Corsair Vengeance 2400 set (CMY16GX3M2A2400C11R), I end up with settings I just don't like. The CPU voltage gets bumped up from 1.072v to 1.28v, DRAM voltage goes from 1.5v to 1.65v and run the memory controller out of spec voltage wise. Timings go from 9-9-9-24 to 11-13-13-31. All of this is to be expected, of course, except the CPU voltage bump I suppose.

The end result is that I've decided to ignore XMP for the moment and run stock 1333 9-9-9-24 1.5v. The seemingly pointless CPU voltage jump is what gets me the most, since it has direct thermal (and therefore acoustic) repercussions.

I've considered a few scenarios:

1) Run full auto - 1333, 9-9-9-24, 1.5v - and never look back
2) Run 1600, 9-9-9-24, 1.5v and memtest it for a while
3) Run 2400, 11-13-13-31, 1.5v and memtest it for a long while

I know in the end it's probably pointless since it will have almost zero impact on real world perf, so option 1 might be the most appealing.

Whatcha think?

 

[VirtualLarry]

Chances are, on that mobo, it is tying MCE with XMP, so enabling XMP enables MCE, which OCs the CPU, which requires a vcore boost.

 

[i7Baby]

See http://www.corsair.com/en/vengeance...am-2400mhz-c11-memory-kit-cmy16gx3m2a2400c11r

You're getting the voltage and timings that you are supposed to get.

Just leave it with XMP enabled.

 

[voodoodrul]

Yeah. While the memory timings and voltage are indeed correct, the greatly increased thermal output and CPU voltage jump for stock just aren't necessary. I disabled XMP and set the DRAM frequency to 2400, leaving most everything else on auto. This worked much better as it applied the timings and voltage to the memory and only the memory.

 

[BonzaiDuck]

Yeah. While the memory timings and voltage are indeed correct, the greatly increased thermal output and CPU voltage jump for stock just aren't necessary. I disabled XMP and set the DRAM frequency to 2400, leaving most everything else on auto. This worked much better as it applied the timings and voltage to the memory and only the memory.

Geez! "MCE" -- for my generation of boards, it was simply an item choice of the multiplier setting "for all cores."

I thought I discovered something more than a year ago.

I'd been running my RipJaws at stock settings -- manually entered. I came across a Tom's HW discussion, and also got confirmation with e-mail G.SKILL tech-support, noting that XMP doesn't just apply to the four basic timings: it implements values for all the others. G.SKILL told me their XMP settings for the other timings were "more aggressive" but part of their spec.

What happens if you make a note of the 4790's idle and load voltage, VID and other factors -- with the voltage items on "Auto;" then tweak the system manually to get the same result? But we also suspect that "Auto" gives you excessive volts for that chip. I'm thinking you should be able to implement the XMP RAM specs and timings, and then get the CPU out of the equation with manual tweaks -- even if only for stock speeds.