Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ukma!xanth!lll-winken!uunet!iscuva!jimc
From: jimc@iscuva.ISCS.COM (Jim Cathey)
Newsgroups: sci.electronics
Subject: Re: FSF/AT-bus architecture
Message-ID: <2445@iscuva.ISCS.COM>
Date: 6 Apr 89 02:12:31 GMT
References: <5768@ux.cs.man.ac.uk>
Organization: ISC Systems Corporation, Spokane WA
Lines: 29

In article <5768@ux.cs.man.ac.uk> dente@s2.uucp (Colin Dente) writes:
>In response to someone's (sorry - I don't recall who) comment about people
>using the AT bus for anything other than 80x86 boards - well Apollo use it
>in all their latest 'Personal workstations' (i.e. DN3000, 4000, 3500 & 4500)
>and it don't seem to do them no harm.  It's not used for everything (e.g.
>memory) - but then do PC maker's never put fast busses for RAM (he asks,
>thereby displaying 100% lack of knowledge of IBM PCs).

The PC bus is not very good, especially when it comes to interrupts.  Who ever
heard of a serious bus that had TTL active-high interrupts!!!  (For those who
don't know, it means you can't have several boards share an interrupt request
line.  This is a serious problem with PC's -- they only support 8 interrupts
total.  For the AT, all they did was add 7 more, and they used most of these
up internally to the box.  The damned bus is _still_ active-high TTL for
interrupts.)

PC bus is a lousy choice for the conceptual successor to the S-100.

For my 2 cents' worth, they should put the designers of the 8259, 8250, and 
765 (8272) chips up against the wall and shoot 'em.  Garbage, one and all.

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