9 Dec
2005
9 Dec
'05
9:13 p.m.
Subject: Re: Legacy apps in Windows/OS X was Re: Old MS-DOS & Win Software
From: ard at p850ug1.demon.co.uk (Tony Duell)
Date: Fri, 09 Dec 2005 18:28:07 +0000 (GMT)
To: cctalk at classiccmp.org
Yes, that circuit is straight out of the intel appnote.
It was quite somethig to take an 8088, 8284(clock
gen), 8205 (aka74138),
8755, 8155 and have a complete 16bitter in 5 or so chips. However, the
IIRC there was a Circuit Cellar article in Byte for a 5-chip machine
using the 8088. The other chips were, IIRC, the clock generator, 8155
(RAM + I/O), 8355 (ROM + I/O) and an Intel RAM chip with multiplexed
address/data buses. The address decoding was done by just connecting the
chip enables to the high-order address lines... Well, I've read the datasbook, I've seen it in
use, but have never
designed with it. What's the problem? It always struck me as a lot nicer
than the 8237 + page registers that IBM used in the PC
think about it. It's a microprocessor with a flat 20bit address and nothing
like the 8088. In some respects is nicer. I had to write a simple debugger
for it using the host for the IO. Very ugly and hard to control.
Allison
9 Dec
9 Dec
9:35 p.m.
On 12/9/2005 at 4:13 PM Allison wrote:
think about it. It's a microprocessor with a flat
20bit address and
nothing
like the 8088. In some respects is nicer. I had to write a simple
debugger
for it using the host for the IO. Very ugly and hard to control.
...and only 2 channels of DMA, where the 8237 would give you 4. One thing
that pretty much doomed it was the announcement of the 80286 with 16M
addressing capabilities, which means the 8089 wouldn't cover the address
space. The instruction set was basically increment, decrement, add, AND,
OR, NOT and a couple of bit test and set/clear operations--along with the
usual conditional jumps and a CALL, but no stack, no subtract and no
shifts. Basically a program-it-yourself DMA controller.
Cheers,
Chuck
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