SWOS & Zool use chipmem for RAM expansion. In some cases with some boards, the mem is slower, and for some reason when the system is booted/mmu/etc... it can be much slower (hence the recurrent swos slowdown bug reports). The problem cannot be fixed (Bert knows better than me about that)
On the other hand, some games can be much faster, e.g. when expansion mem is relocated to real fastmem (check Chaos Engine CD32 or Nick Faldo's Golf CD32 or Body Blows AGA to see what I mean) or that caches disabling has been removed by whdload slave and cache bugs properly fixed.