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FSB backwards-compatible? new
      #20563 - 23/09/04 05:48 PM
Most P4 mobos around now say in the specs that they will take a CPU with 533 or 800 fsb.

Will these work with one of the older P4s with 400 fsb? I don't need a lot of power and I'm looking to buy a cheap chip on Ebay and put it in a more modern board (not sure which yet, but they all seem to say 533/800).

I know that there was the brief socket 423 period, and those CPUs won't fit. But how about something like a 1.8 or 2.0 Ghz, socket 478 Northwood with 400 fsb? Will a mobo that says it wants 533 or 800 run it OK?


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Peter C
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Joined: 08/01/04
Posts: 3054
Loc: London, England
Re: FSB backwards-compatible? new [Re: Wurlitzer]
      #20571 - 23/09/04 06:08 PM

Or to be more precise, I don't think that all 800Mhz mobos will run at lower speeds.

I might be wrong, maybe there are some 800Mhz CPUs that won't run at lower Mhz, but I do know that I have seen something about such restrictions in the last 6 months.

Certainly, you need to be carefull. I think I'd look for the slowest P4 that does run at 800Mhz.



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All Funked Up

Joined: 01/09/04
Posts: 1581
Loc: Australia
Re: FSB backwards-compatible? [Re: Wurlitzer]
      #20816 - 24/09/04 12:39 AM
Yes this should not be a problem at all in most instances.

Intel 848P chipset supports 400/533/800 FSB

Intel 865P chipset supports 400/533 FSB

Intel 865PE chipset supports 400/533/800 FSB

Be careful with 875P mobos as these don't support 400 FSB CPU's. But older (bargains on ebay) 845E + 845PE mobos will support 400/533 but unlikely to support 800 FSB CPU's.

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Rick Taylor
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Joined: 22/02/04
Posts: 2389
Loc: Chicago
Re: FSB backwards-compatible? new [Re: UNIT393]
      #20818 - 24/09/04 12:47 AM
Past a certain point the price difference is going to be negligible anyway.

Do a search on the processor or motherboard here..^ it'll give you a listing of compatible products.


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