Path: utzoo!attcan!uunet!husc6!ogccse!littlei!omepd!mipos3!cadavr!dbraun
From: dbraun@cadavr.intel.com (Doug Braun ~)
Newsgroups: comp.os.cpm
Subject: Re: MEX Overlays and SCSI Implementations
Message-ID: <3193@mipos3.intel.com>
Date: 15 Nov 88 17:59:06 GMT
References: <8811140554.AA25836@ucbvax.Berkeley.EDU>
Sender: news@mipos3.intel.com
Reply-To: dbraun@cadavr.UUCP (Doug Braun ~)
Organization: Corporate CAD, INTeL Corporation, Santa Clara, CA
Lines: 40

In article <8811140554.AA25836@ucbvax.Berkeley.EDU> RALPH@UHHEPG.BITNET writes:

>I am comtemplating adding a hard-disk to my system.
>There isn't anything on the market (no surprise in the case of a self-built
>computer with a non-standard bus). I see two good options:

(option a. deleted)

>b. Build my own SCSI controller. As far as I understand SCSI is
>just a glorified parallel port and an interface definition. There are
>(supposedly) dedicated SCSI controller chips. And one could add DMA (with the
>Z80-DMA chip, or with the built-in DMAs in the Z280). Advantage: nice, clean
>design. Can be made to be real fast (DMA). Can implement a real nice driver in
>the BIOS. Can connect more than just disk drives to the SCSI bus (tape drives
>and laser printers come to my mind). Disadvantage: Lots of work. SCSI disk
>drives are more expensive. Again, who has experiences with this? Which
>SCSI controller chips and disk drives are recommended?

I did just this for my one-of-a-kind CPM system, and it has worked out
very well.  The SCSI Host Adapter is indeed a glorified parallel port,
and I built one from 6 or so TTL chips.  If you used one of those SCSI
controller chips, the design wuld probably be even simpler.

For a controller, there are several places to get SCSI-to-ST506 controller
cards.  I have one made by Shugart (before they went away).  There
are several others readily available, for about $80 or so.  I have
also had a SCSI tape drive hooked up to my system.  This was very easy to do.
I also use the same controller (I have two) on a PC with a PC host adapter.

If this approach sounds worthwhile to you (or anyone else), send me mail,
and I will tell you more.

Doug Braun				Intel Corp CAD
					408 765-4279

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