what X86 can be replaced by RB1000?????

I have replaced all my pre-Pentium4 boxes with RB1000 and they are doing their jobs very well, but I would like to know (before I actually try) how about replacing any post-Pentum3 boxes???

Do you have any experience with it?

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Replaced my P3 1000Mhz ( 80-100% load) with RB1000 ( 10-40% (spikes) load).