If you have the BX chipset you'll be limited to 100MHz FSB on an OEM board. The fastest common processor for that was the 850, there was also a rare 1000E and an ultra-rare 900E. In fact you can get the 1000E (as opposed to the better performing, cheaper 1000EB which ran at 133MHz FSB) for around $130 in the Slot 1 form, no need for a slotket.
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