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overclocking + power requirements

K

kaoman

n00b
Joined
Aug 9, 2004
Messages
50
I have a 3.0e E0 at 3.75ghz 15x250fsb running stock 1.375 vcore on an AI7 w/ 2x512 BH5 using 5:4 divider and lowest latencies, vdimm 3.2v. I've also got an unlocked and overclocked 6800, 3 hard drives, and a Koolance Exos. All on a 350w Enermax PSU.

Now I've seen several setups with similar power requirements on 450+w power supplies but my Enermax has been rock solid and stability has always been there. Until I start hitting the 3.8-4.0ghz region.

My question is - are high and steady voltage rails with my current setup any indication that getting a more powerful PSU will do absolutely nothing for improving my overclocking? Or are steady voltage rails and power requirements unrelated? If I draw near or greater than 350w or whatever the real world max output my PSU can provide, is there any sign besides a system crash that will tell me so? Because if its sagging voltage rails, I'm not seeing any, which would indicate my PSU is fine and I've simply hit the max for my motherboard or processor. I'd like to know before I drop $75 on something that possibly will only boost my electric bill.
 
There are 3 potential culprits: CPU, CPU Regulator, and PSU.

The CPU could simply have reached it's highest OC at 3.75. CPU's can vary and one may have a substantially different ability to reach high speeds over another. If you have a friend with a similar system that hits higher speeds, try your CPU in his system.

A few quick calcs and a look at the PSU will tell you if it's the problem. According to Intel's datasheets, the CPU is supposed to draw 78A at it's stock speed and voltage. At 1.375V, assuming an 80% efficient VR, theis means that the CPU will draw about 10A from the PSU 12V rail. Odds are your drawing a lot more current (since you're OC'ing), probably 90A or so. This equates to about 12A from 12V. These numbers can vary depending on the actual processor current load and the efficiency of the VR that Abit used. 80% might be a little optimistic. The lower the efficiency, the higher the 12V current draw. In any case, take the high number (12A) and compare that to the rating on the PSU. If the PSU has 1 12V rail, you might be overloading it with all the other peripherals and fans. Good supplies will have a separate rail for the CPU using the 2x2 power connector.

The CPU VR is the trickiest to figure out. Depending on how well it's designed, it might be fine, but it could also be overheating (due to too much current) or going out of regulation briefly (again due to current load). Without going into a lab, the best way to tell is use a known CPU that can hit better than 3.75GHz and a PSU with high current 12V supplies.
 
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