If you have a board that can accept the newer PIIIs, ( called Coppermines ) I'd probably go with one of those. If your MB can't take coppermines the fastest Katami available was the 600. If you are using Windows 98, 95, ME adding more RAM won't make a bit of difference for AH. (Complicated but it boils down to Win9x being unable to effectively use more than 128 MB of Ram.) Your video card is top notch and will benefit from a faster processor tremendiously.
Since you have PC 100 ram you will want to be sure that you get a 100 MHz version of the Coppermine. You will also likely need the slot1 version of the PIII. (They DO make a converter board for Socket 370 to slot 1 though, so this isn't too critical.) The fastest 100 Mhz version that I'm aware of is the 850 Mhz. I think that it is only available in socket 370 though.
First of all, what model of Abit board do you have? You will probably need to upgrade the bios to accept a faster processor. Before I say anything else we better find this out so I don't lead you astray.
(You asked, so I'll tell you the hard facts. The AMD Athlon will EASILY outperform the PIII in AH. The Athlon is MUCH more powerful than the PIII for floating point calculations, which is what AH makes heavy use of. If you do decide to go with an Athlon though you will need a new MB and likely a modem. Since you will be changing MBs it is HIGHLY recommended you reformat your hard drive and do a clean install of your OS. This basically means that you will lose everything unless you burn it to CD or put it on a zip disk etc.)
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bloom25
THUNDERBIRDS
