Will a MMX-enabled 3DNOW-featured on-chip-L2-cache-equipped AMD K6-2+ beat old school P54C by per MHz performance in Super PI?
NO.
Here is a summary of the tests I've done on P54C, P55C, M2 and K6-2+ CPUs. The P5A-B mobo, 384MB ECC PC100 SDRAM, XP system. Ran Super PI on RAM disk at least 3 times in each case. P55C wasn't stable at 250MHz as you can tell from the range of time cost and I can't find x2.5 jumper settings for K6-2+.
NO.
Here is a summary of the tests I've done on P54C, P55C, M2 and K6-2+ CPUs. The P5A-B mobo, 384MB ECC PC100 SDRAM, XP system. Ran Super PI on RAM disk at least 3 times in each case. P55C wasn't stable at 250MHz as you can tell from the range of time cost and I can't find x2.5 jumper settings for K6-2+.