Should work @ 66 MHz, anything else is chance

For the most part, EDO was pretty standard stuff - mix & match was (is) no problem. Overclocking always introduces more chance, though. The only way to know is to give it a try.

I don't know anything about the 5177 mobo. Is that an MVP3 board, where you can run the bus at 100 MHz and the RAM at 66? I think it would be a toss-up, performance-wise, between 2.5*75 and 2*100. On the one hand, you'd have both the L2 cache and the RAM at 75, but on the other hand, you have the L2 at 100 MHz, and the RAM at 66. I don't think a lot of the old 66 MHz chips work on a 100 MHz bus, though.