Hello!
The 68000 can't use the 68881 like the 68020/68030 (must be adresses like a separate I/O device).Sorry, but I probably miss something... I'm a newbie with FPU. I was thinking that FPU calls were always F-instructions...
Yes, that's true. It's just that the 68000/68010 don't have the communication protocol implemented to speak directly with the 68881.
Are the FPU instructions different between 68000+68881, 68030+68881 and 68RC040 ?
No, they are the same.
What do you mean by special addressing for the 68000 ?
Every F-Instruction on 68000/68010 generate a line-F-trap and must then be handled in software (e.g. move the data to/from the 68881 registers, setup instructions and so on). That's slow and complicated (imagine that EVERY FPU instruction generate a trap).
If the software address the 68881 directly it's much faster (but you need a compiler that can handle this).
Regards, Frank -- ATARI FALCON 060 // MILAN 060 ----------------------------- http://sparemint.org/ e-Mail: fnaumann@boerde.de