Quote Originally Posted by LennyRhys View Post
I think I may have borked my windows installation already - diagnostic mode plays funny with restarting. When I open up msconfig and select diagnostic mode, it takes about 30 seconds to actually get there, and the "Msconfig: Not Responding" is displayed at the top in the meantime. After restarting my system, it powers down before POST then up again as if there has been a fault, but it keeps trundling along happily and when in windows it sometimes detects a really random amount of memory, like 3.7GB, and I must have inadvertently run the test with about 3GB, hence the low GFlops. I've since managed to get diagnostic mode working properly/seeing all memory, but it's very temperamental...

Regarding GFlops: my main problem is that GFlops are going up and down with no change to voltage whatsoever... it's really annoying. Today I did two runs (at different times, with several restarts in between) with the exact same voltages of 1.4125 vcore/1.35 QPI, but I mysteriously lost 4GFlops somewhere along the line. Every single setting in BIOS was unchanged.

Thanks for chipping in pilsy.
Memory dropping out like that is usually a result of not enough QPI voltage.
Every IMC has a 'drift' associated with it, and the motherboard checks your tWR latency, and then sets an 'estimate' for your tRL latencies. Each memory channel has its own tRL, and it's normal for your dimm slots that are physically further away from your cpu to need higher latency, as the signals take longer to go back and fourth due to the increased physical distance.
tRL can and will CHANGE with every boot, unless you set it manually, and is one of the reasons why there are fluctuations in GFlops. This is because the internal resistance of your transistors will change depending on gate voltage and temperature.
This is why you will have a session where everything seems ok, then you have an error, and it never seems to work again. Your chip hit a temperature that increased the internal resistance of your transistors. This is usually temporary, and can be fixed with a full power down and power cutoff via the psu switch. Leave the machine off for a good 5 minutes to allow the cpu to discharge and cool off. Keep in mind, the same things can apply to the power delivery system of the motherboard itself!

Increasing QPI voltage can help mitigate the drift within an IMC, but it will not eliminate it. Make sure your cpu is nice and cool, and don't go overboard on the voltages for an extended period of time!

I highly suggest you manually set your ram timings, and try to figure out the sweet spot for tWR.

The 'power down' thing you described is actually a 'memory recheck' feature that most x58 boards have now. It's directly related to a memory channel dropout on post, and the motherboard resets and loosens tRL latencies in an attempt to compensate.