Maybe we should comment these lines for now, and recode this better in the next release, no ?
I guess much better thing to do (than randomly switching the cache on/off) is to figure out what exactly works better without the cache and why. Perhaps your 030 cycles are fine but the DSP : CPU ratio is wrong. Because as far as I remember, every demo runs with instruction cache but on the other hand, I can very well imagine plethora of failing DSP demos without 030 instruction cache, where DSP is sending polygon data too fast for CPU to process.