Originally Posted by demolition
It can approach 100% compatibility and if you have the original chip schematics (or high res scans of the die) it can be made 100%, but it obviously cannot be more compatible than the original.
Oh yes, it can. There was no 680x0 compatible with all other 680x0. The 68000 is the least compatible of them all as it cannot execute 68020+ code. The 68010 put some instructions into supervisor mode that on the 68000 were user mode instructions => incompatible. The 020 added loads of stuff (including an FPU) and an instruction cache => no more self-modifying code, incompatible. The 040 dropped some of the 020/882 instructions again and added some new => incompatible. The 060 dropped even more instructions => incompatible.
Now the vampire on the other hand has transparent caches. If you modify code, the dcache will notify the icache and the code in the icache will mark the relevant code as "dirty". Self-modifying code is no problem => more compatible than any other 020+. The vampire has ALL instructions of ALL 68000 and 68020 and thus is more compatible than 040 and 060. You don't need an 040.library or 060.library to use the vampire CPU.