Is L2 cache size important?

I've run Knoppix on many systems from P-166 and K6-200 up to Athlons. I recently tried Knoppix on 2 PIIs (300, 450). Booting took about as long as I expected but both systems seemed to run much faster than I expected. PIIs have 512k L2 cache; could that be the reason?

Yes the faster the processor the larger the cache the less disc access that has to be done, the same with RAM the more the better with enough it will never even use the /swap partition.