6 Aug
2006
6 Aug
'06
4:06 p.m.
On Sunday 06 August 2006 03:05 pm, Chuck Guzis wrote:
On 8/6/2006 at 10:39 AM Don wrote:
Yeah, but...
Back around 1970 or 1971 I got a hold of my first TTL data book, which I
still have. And in times when I had some leisure to play with ideas, I
worked my way laboriously through some vague notions of what it might take to
"build a computer". What info I could find back then was mostly of a very
general nature, out of library books and such, and when it came to actual
machine architecture I really had no clue whatsoever. And the best I could
come up with, for something that promised to be vaguely functional,
would've used about 800-900 TTL chips. It's probably a good thing that I
never actually started to build such a thing.
I was rather pleased to see a short mention in a magazine at one point back
there someplace of a guy's homebrew TTL computer, which as it turned out
also used about 900 TTL chips. There was a picture, of this thing spread
out across the floor, where his cat had knocked it (and having a cat here
that's currently into sometimes being a real PITA when she goes into
"predator mode" I can understand now how such a thing would happen. :-) As
the article pointed out, when it ended up there it still worked, so he left
it there.
That was one heck of a lot of boards and wire-wrapping and power distribution
and cabinetry and not very much flexibility and probably a whole lot of other
issues that I was not aware of in my relatively ignorant state in those days.
Then that "Mark-8" was published in Radio-Electronics. And the Altair a bit
later. And when I first looked at the 8080, I really wasn't all that
impressed. I mean, you had to feed the thing those silly "machine code"
instructions while the thing I'd been envisioning back then would take it in
_ASCII_ (!) which, of course, was a lot of the reason for the
inflexibility, but I didn't know any better back then.
But eventually I came around...
Mostly because you could do SO much more with not really all that much in
terms of hardware.
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.
Yup.
One valuable aspect of the 8008 lost was the treatment
of 00 and FF as HALT
instructions.
I'd still liked to have seen somewhat more orthagonality in the instruction
set, and maybe a bit additional, like relative jumps, one of the things I
do like about the z80. I'd like to be able to use DE or BC as many ways as
you can use HL for example. The z80 added stuff I've never personally found
all that useful otherwise, and have never used the index registers (yet) or
the alternate set, all that much.
And the lack of orthagonality or symmetry is something that I've also noticed
in a lot of the peripheral chips as well. Write-only registers that I can't
read back? WTF? Address space was never that much of a scarce commodity as
far as I can see.
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).
The LSI-11 was my first exposure to a "real" computer in terms of something I
could actually get my hands on and try and do stuff with. I think I even
still have a "quick reference card" in my desk somewhere. And although the
hardware was very weird by comparison with what I'd already wrapped my brain
around (and my one attempt to interface to that bus was not successful), the
software side of it seemed *so* much better than that intel stuff. Of
course, trying to get a grip on RT-11 and the stuff they seemed to sort of
assumed you'd know about was yet another matter.
Sometimes, the actions of the people inside the micro
business made me
wonder.
Sometimes? :-)
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.
Mainframe and mini people knew about a lot of stuff, and I'm sure that this
is only one item on a potentially very long list, but somehow that knowledge
never seemed to transfer over.
For some reason I'm reminded of the stage kids go through when they get to a
certain age (and ain't *I* sounding like "the old phart" here :-) where all
of a sudden they start having all these *wonderful* insights into all sorts
of things, and come to the (usually erroneous) conclusion that their parents
and other people "just don't see it" for some reason, and usually don't
have
a clue about what else might be considered in whatever the context is that
they might perhaps be missing.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin