CPU underclocking

  squillary 04:51 12 Mar 2007

This may be a new twist...

A friend bought a faster AMD processor suitable for their motherboard - a second user item from ebay, so there was obviously some risked attached.

On installation it was unstable at 200MHz FSB. Also unstable at 166... and at 133... and only barely stable at 100MHz FSB. Oh dear. Instead of running at 2.2GHz (XP3200+) it runs at 1GHz (XPno idea but slower than the original processor).

Attempts have been made to clean the processor up and it's stable now but only at this slowest FSB setting.

This is all way over my head so I come here for advice.

The clock multiplier is being set to "Auto" for each FSB speed. Is it possible to set the multiplier manually at a lower setting in order to obtain a sub-optimal-but-stable processor at one of the higher FSB speeds? (Does that question even make sense?!).

What I'm getting at is, the processor may not be stable at 200MHz FSB with a clock multiplier of 11, but maybe it will be at a multiplier of 10. Is there some particular step change of multiplier that has to be used - that is, can we try 10.9, 10.8, 10.7 etc or do we have to change it from 11 to 10 then 9 or what?

Are we flogging a dead horse even comtemplating this idea?

Clearly, I don't even understand my own question, but I hope to understand the answer (with a bit of luck). All replies appreciated.

  hzhzhzhz 08:31 12 Mar 2007

Stick to whole multiplier numbers.

  Aspman 12:28 12 Mar 2007

Does the mobo support the faster CPU?

Does it require a BIOS update?

  squillary 14:19 12 Mar 2007

The MB certainly does support the faster CPU according to the manufacturers site and does not require a BIOS update - fully confirmed.

Regarding whole number multiplier numbers, is there a technical reason for this or not? I'm aware that at some FSB speeds the automatic multiplier is not a whole number (13.5 in one case I think) so it doesn't seem to be a hard and fast rule.

Instead of people guessing, has anyone actually had to try this and know for certain? I'm quite a good guesser myself, but I'm asking for direct experience.

  jam500 16:18 12 Mar 2007

Sorry i dont have direct experiance, But my brother had problems with his new install of an AMD processor i.e unstable, We only got it sorted because the memory etc was linked to the FSB and was causing all sorts of problems. Maybe it is worth looking at all the things that are affected by the FSB. I hope this helps.

  squillary 16:54 12 Mar 2007

Interesting point about RAM. I think it's got PC2700 though it does support PC3200. Let me ask that question and come back.

What other components are sensitive to FSB speed?

  squillary 12:58 13 Mar 2007

PC2700 runs at 333MHz (for 166MHz FSB), PC3200 at 400MHz (200MHz FSB).

I think jam500 has hit the nail on the head here. Many thanks. What other components are sensitive to FSB speed? Where do I search to find out?

  jam500 15:03 13 Mar 2007

Your graphics card slot is also FSB related, I think that is all.

  squillary 18:19 13 Mar 2007

It has an ATI Radeon 9500 graphics card plugged into an AGPx8 slot - that should be ok, shouldn't it? The spec at click here doesn't enlighten me at all. Is it ok?

Thanks again.

  squillary 19:32 19 Mar 2007

PC3200 RAM installed and it didn't help, unfortunately. Reverted to the original processor and all's back to normal, albeit with a bit more RAM (faster to but not accessed at rate that shows any benefit).

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