Socket 604 upgrade question

[Lorne]

I have a SM P4DSE with twin 1.8Ghz Xeons. ( Changing MB in this system is not an option at this time or probably ever.)
The website info and manual show 400FSB
I have a friend with a 3Ghz 800FSB who might free it to me

I also see online some real cheap pricing now but all are 533-800FSB.
What would happen if those are dropped into this MB?
I dont have time to experament.

 

[Ben90]

They would work, but at a severely reduced speed. The core clock is a product of FSB * CPUMultiplier. Since your 400MT/s FSB is quad pumped, it is effectively running at 100Mhz. Your Xeons use a x18 multiplier. 100Mhz * 18 = 1.8Ghz.

Your friend's 3Ghz Xeon uses a 200Mhz FSB making the multiplier 15. Putting that into your MB would have it run at 100*15 = 1.5Ghz. Slower than your current processors

Unfortunately you seem to be in a rut because there are really no real upgrade options for a 400FSB motherboard. I strongly urge you to reconsider upgrading your base platform because a modern single socket motherboard with a cheap Xeon and two sticks of DDR3 would be both faster and cheaper than paying for a retail socket 604 processor.

 

[taltamir]

They would work, but at a severely reduced speed. The core clock is a product of FSB * CPUMultiplier. Since your 400MT/s FSB is quad pumped, it is effectively running at 100Mhz. Your Xeons use a x18 multiplier. 100Mhz * 18 = 1.8Ghz.

this is the standards answer, however I remember finding out that at least on RAM on those old P4 systems you cannot put 533 to 800 mhz ram into the 400 mhz mobos. Which is an odd exception, I don't know if the same applies to CPUs in this case.
There are always possibilities for other things causing incompatibility with newer chips though, the bios has to be update to support newer chips (and yet a bios update might not be available), the vrms might not provide sufficient power, etc.

So IF it just works (and it probably would), then what you said applies... which is, that it will be knocked down from 3ghz to 1.8ghz

 

[Lorne]

Sadly Ive tried talking them into a upgrade but they are "If its working then it doesnt need to be touched" but they dont have to use the intencely slow POS.

It is on the last BOIS and getting support from SM is non existant

Thanks guys.