From: Keith R. Williams
Subject: Re: ISA IRQ signal active how long?
Date: Mon, 7 Oct 2002 22:05:45 -0400
References: <3D9FCE3B.60DAB50D@mfi.net> <3DA10F89.6A82CD2@mfi.net>
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In article <3DA10F89.6A82CD2@mfi.net>, email@example.com says...
> "Keith R. Williams" wrote:
> > In article <3D9FCE3B.60DAB50D@mfi.net>, firstname.lastname@example.org says...
> > > Ralph Wade Phillips wrote:
> > > >
> > > > Howdy!
> > > >
> > > > "Keith R. Williams" wrote in message
> > > > news:MPG.email@example.com...
> > > > > In article ,
> > > > > firstname.lastname@example.org says...
> > > > > > Howdy!
> > > > >
> > > > > > PC standard is edge-triggered, not level-sensitive, for ISA
> > > > card,
> > > > > > IIRC. This (and the active-high) I've ranted about since, oh, about
> > > > 1981
> > > > >
> > > > > I ranted about this before '81. I couldn't believe the PC
> > > > > designers made such a *stupid* mistake. Indeed this isn't the
> > > > > only transgression. The designers had no idea how to design with
> > > > > TTL.
> > > >
> > > > Eh. The PC wasn't introduced until 1981. Late 1981, for that
> > > > matter. And that was with a (for IBM!) very short lead time - 6 months,
> > > > IIRC.
> > > >
> > > > RwP
> > >
> > > Yes, but the ISA buss was a holdover from a word processing system
> > > based on the 8085 that used the same five slot case as the original PC.
> > What system would that be? The Data-Toaster, err Master,
> > certainly had nothing in common with the PC. The Delay-Writer
> > may have, but only after the PC was already popular.
> > > Remember the little metal door with a screw in the back that covered
> > > nothing? There was a battery there in the word processor.
> > No I don't. Perhaps you'd like to remind us.
> > > The video
> > > board and floppy drive controller board was the same in both systems. I
> > > scrapped several of the word processors, because no one wanted them.
> > > Now, i wish I still had one to show people where the PC came from.
> > Perhaps *after* the 5150, but not before. There was nothing in
> > common with any other product. The PC was done by an Independant
> > Business Unit, and did whatever to go cheap. ...even stupid
> > designs.
> > ----
> > Keith
> I got the information from a retired IBM engineer. He told me they
> were not allowed to have a new case designed, and chose the cabinet form
> a low end word processing system, including the original single sided
This is suspicious (I'm not a retired IBM engineer - quite yet).
The drives were rock-standard parts available anywhere at the
time. The casing was advertised to be custom built for the
application (all the crap about cooling from the slots in the
front). I've *never* seen another IBM product with the casing of
the original 5150.
> They wouldn't even let them commit the motherboard to copper,
> till they had a working, wire wrapped prototype.
Common in those days. PWBs were expensive to develop and
simulations, well weren't. WireWrap was simple and cheap to do
and very easy to modify. I see no contradiction here. Perhaps
their original board went into other casing. Again, I've never
seen any other IBM product built with the crappy casing of a PC1.
Sure, it was bullet-proof, but the fit&finish was junk for its
> That was the reason
> for using the existing video board with a printer port, and why the PC,
> XT, and AT had the IEC connector to power the monitor.
I've never seen that video board (I'm assuming you're talking
about the MCA board) used in any previous product either. It was
a rather crude board, but worked reasonably well. The
DisplayWriters of the time were far better.
BTW, the IEC connector was there to reduce the number of outlets
required. It had nothing to do with the adapter, though the
monochrome monitor was *very* poorly designed. BTW, I don't know
any other IBM device that used that monitor either. It would be
banished from any project I was part of. What a *stupid* design
(though was a foreshadowing of the PC world).
> The Floppy
> controller board came from the same design. I have seen the machines,
> and scrapped two of them. The motherboard in the word processor had
> several of the typical aluminum IBM IC packages.
You're going to have to be more specific, before I can even try
to understand what you're talking about. Model numbers (four
digits) would be really nice.
> The market research said they would NEVER sell 1000 units.
Nonsense. The number was more on the order of 25000 (give or
take a zero) units. At 1000 units it would have *never* been
done. At 2500000 units M$ would never exist.
Something like 10000 units were sold to IBM employees on the
"first day" sale. Your numbers are plain wrong.
> The PC was to be sold to small businesses to get them used
> to a computer, so they could be talked into buying a mini computer when
> they hit the meager limits of the PC.
Nonsense. It was an Independant Business Unit set up to explore
these silly microprocessor thingies. Apple rejoiced! It made
their marketing plan a reality.
> Why would one of the designers of the PC lie about the history?
Lie? I'm not talking about lying. Perhaps he wasn't so close as
you think? Perhaps you can give me a name? ...a location?
> I met him when he wanted his original PC fixed.
If he were a participant, he'd have fixed it himself. Sheesh,
the things were a piece of cake to fix. All the logic is "right
there" in small packages.
> It was one of the
> prototypes, and had an IBM property tag on it. He said it was still in
> his office when he retired, and they told him to take it with him, or
> throw it away. He needed a floppy controller card, and the owner of a
> computer store was yelling at the old man telling him to throw the piece
> of shit in the dumpster because no one, anywhere had any parts for his
> computer. He was almost in tears from the abuse, so I interrupted them
> and asked what he needed. He told me, and they guy started yelling at
> him again. I told him I had several good cards, and offered to fix it.
> He told me he had it in his car, so I went to get it, and took it home
> to fix it. When he came to my home to pick it up we talked for several
> hours about the history of the PC and the machines that followed. I
> moved a couple years ago, and in the move I lost my paper address book.
> If I could find him, i would put you in touch with him so you could tell
> him he was wrong.
I'm not saying *he* was wrong. I have no way of arguing with