As I mentioned early, I have bought this CPU after my last exam. AMD AthlonII x4 640 C3+ASRock 880GM-LE+2x 2GB Team Elite DDR3 1333 CL9. The performance was moderate but this computer costs are low, very cheap!! First of all, I tried the first thing, which was lowering the vcore voltage and dram voltage. The most interesting thing was by default dram was running at ddr3 1333, that’s right! But if you look more details of dram, timing was CL9-12-12-30-33@ 1.71V. Hey, ASRock were you born to be burning memory?? Although 1.71V was not the maximum stable voltage for ddr3, it was as low as 1.35v to maximum stable 1.80v. On the other hand, the memory was labelled as CL9-9-9-24. Why were you running them as CL9-12-12-30-33, they were on the memory support list! So, I manually set dram voltage to be 1.48V the minimum for this motherboard, then I set the vcore from 1.375V to 1.175V same as CPU-NB voltage. If you want to ask me why should I set at strange value?? Because I wonder why some motherboard (this problem also in crosshair formula IV) make the vcore higher than the value set in BIOS (e.g. 1.375V will display as 1.416V in windows CPU-Z), moreover Gigabyte AMD motherboard use 1.475V as default auto vcore, so high!!!
For the next step, I am going to find the best stable CPU speed (p.s. with lower vcore, lower power consumption and lower temperature). What I found was the cpu speed can only run stable with 220×15=3300 @1.325V, dram 1466 CL8-8-8-22-30 @1.48V. This is the fastest and energy efficient speed. CPU temperature max 63 degree and DRAM 100% pass ok in memtest 86+ with 50xx Mb/s bandwidth. I will keep testing the peak of this 640 C3, currently working on 240×14=3360 @1.325V, dram 1600 CL9-9-9-25-34 @1.48V, but blue screen was found after 10mins of prime95 stress stability test. So, increase a little vcore to 1.350V, I hope it could be stable~