How CPU's work (was Re: Hi, I'm new...)
cclist at sydex.com
Sun Aug 6 14:05:14 CDT 2006
On 8/6/2006 at 10:39 AM Don wrote:
>The "problem" with the MPU was putting it in a "computer".
...and that's really the nub of my argument. I have no quibble with the
application of an MPU to play MP3s, run a scanner or traffic signal, but
the huge mistake IMOHO, was trying to turn them into "Gemeral Purpose
Computers". I'm not proposing that large-scale integration was wrong--it
alone would reduce the size of your "washing machine" to a deskop box.
Heck, my mouse has a PIC in it--but I'm not about to try to put a word
processor or a DBMS on it. We're still living with the legacy of the 8080
and CP/M in Windows.
Not your post, but Dave's. While it's true that there were a significant
number of major differences between the 8008 and the 8080, the architecture
from a software point of view was set in the 8008. Accumulator, B,C,D,E
registers; H,L handled as a pair to address memory; basic instruction
layout, etc. The addion of SP and 16-bit addressing was a welcome
addition, as were 16 bit adds and loads and 256 I/O ports, but to my eye,
the 8080 looked like a tarted-up 8008. One valuable aspect of the 8008
lost was the treatment of 00 and FF as HALT instructions.
Also, I'm not saying that the CP1600 was a speed demon--AFAIK, aside fromt
he Activision games, it found no general application. Yet, from a
programming standpoint, the closest thing to it prior to the 68000 was the
LSI-11 (not a speed demon either).
Sometimes, the actions of the people inside the micro business made me
wonder. When I put my first hard disk (a 14-inch Shugart) on an 8085, I
noticed that there was no one offering disk backup utilities for micros. I
still have the rejection letter (along with the 8" floppy) from Lifeboat
saying that they didn't think there was any market for a hard disk backup
package. What I found incredible was the reinvention of mistakes. How
long was it before the micro database people realized that atomic logging
of database operations was worse than useless--that one had to log entire
transactions? Mainframe people knew that before there were even micros.
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