My Second Mac

Sridhar Ayengar ploopster at
Sun Jan 7 16:20:14 CST 2007

Scott Quinn wrote:
> We're talking about two slightly different things here, though- 68000 
> (while it did not have provisions for easily running 6800 code) had a 
> common-mode so that programs built on the 68040 could run on the 68000, 
> but you can also have code that requires instructions (or other things) 
> added on later 68000-series processors, similar to Intel (variable 
> 286-style segments, the copy-on-write provision of the 80486, etc.). The 
> transition between 68000 and PPC was more like the Intel gap between the 
> x86 and the 960 - they are completely different processors with no 
> common heritage (the common heritage piece was provided by Apple in 
> firmware). I haven't worked with them, but AFAIK the new embedded 
> versions of the 68000 (ColdFire?) maintain the tradition of working with 
> earlier 68ks (except in a few cases).

Earlier revisions of ColdFire weren't compatible with older 68K.  The 
latest revisions are now compatible enough to work as replacements for 
the 68060.  If memory serves, the ColdFire chips that work for replacing 
an '060 are latest two revisions.

I've seen a ColdFire upgrade board for the Amiga 4000.  It's blazing fast.

Peace...  Sridhar

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