High FSB or CPU Multiplier

[TerryS]

Trying to O/C E8500 on P5K Delux. I reached 4037 MHz at 1.375v (9.5 x 425). 4Gb OCZ RAM at 1066 Mhz. Prime95v238 stable for 12 hours however Flight Sim X crashes after about 30 mins! Through a bit of experimenting I have the system completely stable by increasing the FSB to 445 and reducing the multiplier to 9. This gives 4005 Mhz. Why would there be such a difference in stability if the end result is the CPU running at roughly the same speed with the same voltage? CPUz shows the Vcore at 1.3440v which I believe to be within the specs of the CPU. I intend to run this 24/7 O/C'd so I'm a bit wary of increasing the Vcore any more although the Temps are 25 C idle and 55 C Prime 95. Hope someone can advise as I would like to push the CPU further. (FSX is very CPU intensive and does benefit from higher clock speeds).

Terry

 

[teabagger]

People tend to forget that the stability of an overclock is down to many factors, and not just the cpu or RAM. It could be that your motherboard has an instability hole around the 425MHz mark that was causing issues.

 

[Amonlym]

it could also be the edge of stability for the cpu: once you aproach the limits scaling with volts goes to pot, you love a lot of stability for very little change in freq
My Old X2:

2920Mhz, +0mhz (0% up from 2920), +0v (0% up from 1.425)
2950mhz, +30mhz(1%), +0.05v (3%)
3000mhz, +80mhz (3%), +0.125v (9%)
3100mhz, +180mhz (6%), +0.25v (17.5%)
3180mhz, +260mhz (9%), +0.45v (31.5%)

 

[pugheaven]

Trying to O/C E8500 on P5K Delux. I reached 4037 MHz at 1.375v (9.5 x 425). 4Gb OCZ RAM at 1066 Mhz. Prime95v238 stable for 12 hours however Flight Sim X crashes after about 30 mins! Through a bit of experimenting I have the system completely stable by increasing the FSB to 445 and reducing the multiplier to 9. This gives 4005 Mhz. Why would there be such a difference in stability if the end result is the CPU running at roughly the same speed with the same voltage? CPUz shows the Vcore at 1.3440v which I believe to be within the specs of the CPU. I intend to run this 24/7 O/C'd so I'm a bit wary of increasing the Vcore any more although the Temps are 25 C idle and 55 C Prime 95. Hope someone can advise as I would like to push the CPU further. (FSX is very CPU intensive and does benefit from higher clock speeds).

Terry

Either way fella, you're better off with the higher FSB for bandwidth which will be a bit higher. Usually with higher FSB, instability kicks in, which in your case is the opposite... which like already posted, looks like a stability problemn around the 425mhz region.

I know I can run my FSB at 1511, if I do, nothing, just won't do it... yet I run 24/7 at 1600FSB, really weird!

Cheers
Pug