. . Pentium class chips tend to change core voltages and other tricky things, and the clock multiplier isn't built into the chip as with 486's (which were designed to upgrade older boards) I wouldn't recommend changing to a chip the motherboard wasn't built for, and you need to have the board manual to find out what it supports.
Best to buy a motherboard / chip / memory set left from someone's 500-MHz upgrade. Should be plenty of 233 / 333-MHz stuff floating around somewhere.
Do I remember Evergreen going belly-up, but someone took over the processor upgrades? Or was that Kingston dropping theirs (along with everything else except memory products)?