vladgur:
SS7 is 100Mhz FSB/PC100 and has AGP, although the CPU sockets are the same. I had a standard K6-III and K6-II in a TX socket 7, but not the K6-3+. I now have 2 3+ @2.1v and an old 2.4v K6-III in my linux server-all 3 SS7. ..and 2 retired K6-III 350s@400.
Make sure your TX has 2-2.2v max for a k6-3+ and 2x multiplier = 6x, which isn't bad at 75, or 83Mhz bus speed. It also has to be MMX capable. The main problem is that the BIOS probably wont handle the 3+, as older SS7 can't. It's actually a notebook CPU, but smokes in a compatable desktop. I have them in 2 Soyo 5EMA+ v1.0 ATX boards, 5/00 BIOS.