I saw an old review of a prototype G4 upgrade from Daystar that had 2m cache vs 1m cache in the production model and the results weren't impressive. Running about 20 apps and benchmarks the 2m cache model only scored a combined 3% faster overall and showed no benefit at all in about half the tests so Daystar dumped the idea because the extra cost wasn't worth it for the minimal benefit on only a handful of apps that were able to utilize the additional cache. The difference in the cache in this test probably had little effect on the outcome. Still, the classic Mac OS is not multi processor aware, so your apps have to be if you want to see any real benefit from the second CPU. It's like running non-Altivec aware apps on a G3. You won't see any real speed difference from a G4.