Hi all, I was hoping someone might be able to help me get the rated speed for my RAM. This is the RAM I have running on a Z97i-PLUS and 4690K: http://www.corsair.com/en-gb/vengea...am-2400mhz-c11-memory-kit-cmy16gx3m2a2400c11a The XMP setting of 2400MHz (11-13-13-31-1.65v) was noticeably unstable in windows and failed memtest almost immediately. Since then I have just been running at 1333MHz. I know the speeds in XMP are not guaranteed as they depend upon your MB and CPU coping as well, but I have paid for faster RAM so I might as well try some tweaking... The XMP description says “XMP DDR3-2401 11-13-13-31-2N-1.65V-1.20V”. I can see that every part of that description corresponds to a change in the bios when I turn on XMP (speed, timings, DRAM voltage) apart from the last “1.20V” which I think is the internal memory controller (IMC) voltage. I can’t see any direct control for the IMC in my bios. Some online sources say that VCCSA (called system agent voltage offset in my bios) controls the IMC voltage, whereas others say its VCCIO (i think called digital I/O offset in my bios). I think both these names might be outdated as things are moved around between different CPU generations. The other problem is that my bios only lists offsets and doesn’t seem to have an absolute voltage readout for either of these values, and I can’t find one in windows tools either (presumably because haswell moved some voltage regulation stuff onto the CPU). The MB manual says these voltages “take the standard value for the CPU by default” but I can’t seem to find what that is. tldr: I think the XMP mode is failing because it can’t automatically set the last voltage to 1.20V. I think that voltage is for the IMC, but don’t know what in my bios corresponds to that. Could anyone familiar with RAM overclocking on haswell offer any advice?
VCCIO is the thing you're after as far as I'm aware. You should be able to get a readout of what its' current value is using HWMONITOR.
Thanks noizdaemon666, in my bios VCCIO is split into analogue and digital but neither show up in HWmonitor. I have attached the readouts: (I manually set a +0.1V offset for VCCSA and a +0.2V offset for VCCIO-a and VCCIO-d here to see if I could identify any voltages by their values) I then tried upping VCCSA and both parts of VCCIO by +0.2V but it was still unstable.
I have the same problem with pretty much the same hardware as you. My machine is so unstable it will fail too boot 4/5 times with XMP enabled. I haven't played with any voltages yet. Ill have a play when I get a chance and let you know
Thanks Cobalt, it will be interesting to hear how you get on. I tried fiddling with the voltages I mentioned previously but nothing seemed to make a difference. I eventually tried the XMP settings with default voltages and lowered the speed until I hit something stable. For me, 2400 booted but gave noticeable problems (steam downloads failing, etc) and failed memtest in seconds. IIRC 2200 seemed OK but failed a 24 hour memtest run, whereas 2133 passed a 48 hour memtest run. I am currently using 2000 to be safe and haven't had any problems, although I know my timings are probably much looser than they could be.
So I had a little play last night, using AI tweaker. It looks like I had bought the 1866Mhz kit, not the 2400mhz. Still it was sat at 1333mhz and when I have tried to enable XMP before it has never worked. After having a look through various pages of settings, I found one for DRAM voltage, which was at AUTO 1.5v. I set it to manual and then 1.51v. Before I had the BCLK at 100mhz, and a multi of 46. Its now sat at 102mhz with a multi of 45, and the DRAM is clocked at 1904mhz (IIRC). I didn't get a chance to run memtest, but I ran Heaven benchmark and it was ok.. I'll do some more testing when I get a chance but I'm totally miffed as to why this now works! Also, AIDA 64 reports VCCSA and VCCIO - couldn't find VCCAIO/VCCIO-a or VCCDIO/VCCIO-d
