I found test program called MemCheck12 and it didn't show any errors from fast ram.
Output from ShowConfig:
RAM:
Node type $A, Attributes $5 (FAST), at $600200-$7FFFFF (~2.0meg)
Node type $A, Attributes $703 (CHIP), at $400-$1FFFFF (~2.0meg)
hmm.. looks like the fast ram memory are does not...