From: "Michael A. Terrell"
Subject: Re: ISA IRQ signal active how long?
Date: Sun, 06 Oct 2002 01:46:35 -0400
Organization: Do I have to? Well, Ok. If you insist!
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Ralph Wade Phillips wrote:
> "Keith R. Williams" wrote in message
> > In article ,
> > email@example.com says...
> > > Howdy!
> > > PC standard is edge-triggered, not level-sensitive, for ISA
> > > IIRC. This (and the active-high) I've ranted about since, oh, about
> > 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,
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.
Remember the little metal door with a screw in the back that covered
nothing? There was a battery there in the word processor. 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.
Michael A. Terrell