Piru wrote:
@Ragoon
The coldfire since core V4e is fully compatible with the 68040. The first generation (5102) was already fully compatible with the 68EC040. It is an enhanced version of the originals 68k (410 MIPS @ 260MHz for actual coldfire and 110 Mips @ 75 MHz for 68060).
They are not compatible.
Supervisor mode is totally different. User mode is different, and even with emulation library loaded the user mode has a small difference which cannot be trapped.
Piru is correct on this. You need to rewrite the ROM to be able to take advantage of even a 4e Core Coldfire.
FWIW, I don't think the author of the Coldfire project had the proper background to complete such a complex design but that's just my opinion.
The biggest problem is that to really use the coldfire you need the OS source code so you can make as much if it coldfire native as possible. The OS would also take up more space since more instructions are needed to do the same thing.
*IF* you rewrite the exec, timer device and some other stuff that's needed just to get the computer started then you can think about using the illegal instruction trap to emulate missing instructions. BTW, someone took the commented disassembly of the exec I made and got it running on a V2 developer board but I haven't spoken with him in a LONG time so I'm not sure what ever became of it.
The addressing modes that can't be emulated were slow and I'm guessing were rarely used (certainly not by most compilers) but the math instructions that are legal but function differently are bound to create some problems. Since identical behavior isn't always required some software would work and some wouldn't.
People that claim a Coldfire wouldn't be faster than an 060 either haven't looked at the benchmark info from Motorola or they are just ignoring it. Extensive code analysis of millions of lines of code showed *at most* a 30% performance drop emulating existing 68K code on older Coldfire chips (V2 core). I also believe that was 68000 code, not 060 code which has fewer incompatibilities. Even if their estimates are optimistic the 4e has added many more instructions and addressing modes over the V2 so it should run 68k code much faster than the V2. Software should be over twice as fast on the 260MHz 4e than on the 75MHz 060. Anything that could be recompiled to native coldfire code would run over 3 times as fast and that's if they don't introduce faster clock speeds. They have mentioned faster clock speeds in the past so I'd expect to see 400+MHz parts within a few years.