@ ThoR
here's the showconfig and muscan of my system
Thanks. Yes, indeed, as I assumed, there is something wrong here. First, your fast RAM is only configured as writethrough, not as copyback, which means that the system runs unnecessarily slow. Second, the I/O space occupied by the XSurf is also configured as writethrough, but it should be cache-inhibited, which is the source of your trouble.
This is *not* the configuration that would be left by my 68060.library (or rather mmu.library) but something else misconfigured the system. What you see here is the configuration that was left by the Os startup through the TTx registers, re-configured probably by MuFastRom (or some other ROM-remapping tool, but likely the latter).
Thus, again: Which version of setpatch is this? Which version of the 68060.library is this? Is the 680x0.library installed? Do you have an ENVARC:MMU-Configuration file? If so, does it contain the line "ClearTTx" at the beginning (it *really should*).
Greetings,
Thomas