Date : Tue, 14 Apr 1992 21:17:30 GMT
From : amethyst!organpipe.uug.arizona.edu!afthree.as.arizona.edu!tom@noao.edu (Thomas J. Trebisky)
Subject: Re: Hard disk for S-100, CP/M
In article <2787@dove.nist.gov> kent@cme.nist.gov writes:
>I have an S-100 based CP/M system. It's purely home-brew, and I can't
>get rid of it since there's too much effort invested in special-purpose
>boards I've built for it. I would like to put a hard disk on it. It has
>a 10 MHz 80186 CPU.
>
>Does anyone have a reccomendation for a controller card? Does anyone make
>them for S-100? Does anyone know how to interface a PC controller card to
>S-100?
Nobody makes anything for S100 anymore, it is just a question of what kind
of controller card you can scrounge up, and if you can reverse engineer it
or find documentation.
Well, if you are really into homebrew, here are two pretty reasonable ways
to go: The first is SCSI (SASI), this is really a pretty simple parallel
interface with a well documentated protocol. I hacked together a simple
interface that worked, based on a 8255 PIO chip, but if I had it to do
again, I would probably just use ttl latches and buffers. Simple hardware
means driving all the scsi states with software, no big deal. You can
push more of the work into hardware if you want, add DMA, make it as complex
as you want to.
Another option is the very popular IDE interface being used in PC's.
A couple reasons this is not as attractive as SCSI: It has a 16-bit data
bus (so if you want this in a Z80 system, forget it). Also the price of
SCSI drives is about the same as IDE drives these days, so why mess with
the IDE jobs -- you also have to pry documentation out of the vendors
(which is not all that hard actually), and once again write a driver/bios
to support it.
Forget homebrewing an MFM interface unless you are a real whiz at designing
phase locked loops and such to build the data separator, go with the
"smart" drives like the SCSI.
Just my opinions after all.
--
Tom Trebisky ttrebisky@as.arizona.edu