Piru is right but I would like to hear what Oliver Hannaford-Day, the board designer, have to say about this.
You rang?
Piru is right, the Coldfire has hardware built in to trap none coldfire compatiable instructions, which it then passes to a software program (if running) which translates it in to a coldfire native version (Like what oxypatcher does for the FPU on 040/060 CPU's) and passes it back to the Coldfire which loads the new instruction inplace of the old one and then continues on with the main program, if it hits another unsupported instruction the process is repeated.
The convertion software is coldfire native and has to be running before an illegal instruction is read, which means it has to be loaded before the kickstart. (Or an AROS coldfire native kickstart needs making)
The last prototype had a flash chip on the board which was designed for this, I want to have a play with a few things so there is no flash chip on this boad, instead there is a large pin header with all the required signals so one can be added later.
It's no 68k CPU. Only later it added more m68k series compatibility, but it still is no m68k.
It is a member of the same family (Freescale just say 68K/Coldfire now) and the Coldfire CPU always had 68K instructions, but only the most common ones, later Coldfire revisions added more 68K instuctions but yes, its still not a drop in replacement, and wont ever be.
I have read that this is required for some fpu instructions only.
The FPU in the Coldfire is totally different from the 68K, Freescale dont class it as a floating point unit, just an Emac, which "does" do maths equations but is very different from a 68K FPU.
(There is a true FPU in the V4e though)
Back to the 68K issue, its basically a bite it and see. When the card is done I will have to run a lot of old and new 68K software through it, see how it reacts.
The CPU might get so bogged down emulating 68K instructions that it would be no faster than a 68060.
But even then if it worked well it would still get launced as the price is expected to be very low and the ability to add 512Meg of SD-Ram would still give it an edge. (And any Coldfire native program would run at full speed (3 times that of a 68060))
