2 May
2009
2 May
'09
1:50 p.m.
On Sat, May 2, 2009 at 15:38, Brent Hilpert <hilpert at cs.ubc.ca> wrote:
Tony Duell wrote:
Keeping in mind as well, that at the the time of the 68000 release ca. '79/80,
16MB=2^24 was a lot of memory. Going beyond 16-bit physical addressing was
warranted in terms of market/economics, the same could not be said for 32-bit
physical addressing for a microprocessor system. 24 bits was a practical
goldilocks solution.
The 32-bit initial architecture provided for future upgrade/compatibility, and
was addressed (pun) in later versions.
Then of course there were those programmers that thought they were
clever, using the top 8 bits to store flags in pointers, etc. Royally
messed up when upgrading to 68020 and up.
Somehow this seemed only a problem on Macs - the "dirty" ROMs issue on
the SE30 and some others. I don't recall the Amiga ever having those
issues, and I have no clue about the Atari...
Joe.
--
Joachim Thiemann :: http://www.tsp.ece.mcgill.ca/~jthiem