E8500 and 500fsb

[onkel]

Hi everyone,
For a while i have had my e8500 OC'ed at 4275MHz 450x9,5 with some 1333MHz corsair 2x1GB memory that were OC'ed a little (1444) in order to run a linked 5/4 divider. Then I upgraded the memory with OCZ 2x2GB that runs at 1600MHz.
On all the different internet forums i see alot of people running 500fsb with the 'new' 45nm generation intel chip. And the nvidia 790i chipset (mine is an XFX 790i ultra) shouldn't have any problems what so ever runing 500fsb either.
So i figured, 500x8,5 = 4250MHz perfect! linked memory with a 5/4 divider = 1600MHz spot on what my memory can run since 2gb dimms are very hard to overclock.

However i just can't seem to get a stable 500fsb. Sometimes after unpluging the power and power up again it boots and runs fine. play games, prime95 etc. Then next time i reboot it won't boot up. Again, power on/off/on/off/on -> bios save&exit and all the sudden it boots up again.
If i drop the fsb to 475 i have no problems.
So my question is? (a) have i hit my cpus max fsb (b) have i hit my motherboards max fsb (c) are there some settings that im missing for running a 500fsb?

According to others on the net it seems that hitting a 500fsb with a E8500 and a 790i based motherboard should be a walk in the park but for some reason it seems impossible for me :frown:

The way i tried to reach 500fsb was to set the cpu speed around stock speed 3.16GHz +- 200MHz, cpu voltage auto, unlink memory and then rise the fsb while keeping the cpu speed down with the multiplier. I think I tried all possible fsb voltage but no luck. It just wont boot.

Any suggestions ?

[jellyrole]

Did you set your RAM voltage instead of leaving it at auto. That helped me maintain when I was trying to go above 2.8GHz on my E6600

[PP Mguire]

Give the CPU a little more juice.

[ahsalloum]

Yes, try increasing voltage by small increments until your system is stable.

[onkel]

Dunno but for some reason I thought that cpu voltage were for rising the actual cpu end frequensy multiplier * fsb and the fsb voltage for inreasing the fsb. But it seems that u you guys are right. I slowly increased the cpu voltage and bang.. all the sudden it boots 10/10 times with 500 fsb. Gonna let it run prime95 for a few hours now, then a few days of gaming. And if I still haven't had any problems then ill bring out the cigar :-D

Thanks alot guys.. ill get back to you in a few days after my 'stability test'.

[PP Mguire]

Giving it more voltage increases stability at higher clocks.

[caldin]

yeah, i OC'ed my E8500 a bit, i just went to 3.8GHz. but it took a couple days messing with voltages and memory timings before i got it 100% stable. and it is still working perfectly, even after a 3000 mile move :P that move had me worried for my machine for a while.

[PP Mguire]

Actualy after reading his post again i realized what the problem was. The CPUs frequency was stable at stock volts but it was the CPUs FSB that wasnt stable. Those chips are 1333fsb and he was running it at 1600. Makes sense now.