[Coco] Tandy Hard Disk Controller

[farna at att.net]

As I recall the Disto controllers were SASI/SCSI compatible. I had one with a 4-n-1 board. Most people used them with SCSI drives because later in the 80s small SCSI drives were the most available, and the older SASI drives were big clunkers. I seem to recall that you had to make a special cable to connect a SASI drive, but that was all. Not sure if there were different drivers (I don't think so) or any software parameters had to be changed -- other than the physical drive specs. 

I did some checking on the web -- SASI (Schugart Associates System Interface) later became SCSI. It was just a host interface, not a controller. It could be connected to several different controllers, usually housed in the drive enclosure. The Tandy CoCo controller could indeed have been a SASI interface. Any controller with a SASI interface could then have been used, not just Shugart. For a pic of one of the controllers, and a schematic of a SASI interface for a 6800/6809 processor, go to http://www.swtpc.com/mholley/SASI/SASI_Hard_Drive.htm. SCSI controllers provide the interface and controller card in one unit, and have some enhanced features over the original SASI. 

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Frank Swygert
Publisher, "American Independent 
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 -------------- Original message ----------------------
Message: 7
Date: Sat, 4 Mar 2006 00:59:50 -0700
From: Willard Goosey <goosey at virgo.sdc.org>
Subject: Re: [Coco] Tandy Hard Disk Controller

>Date: Fri, 3 Mar 2006 18:31:14 -0500 (EST)
>From: "Bill Gunshannon" <billg000 at cs.uofs.edu>

>As long as we're talking about COCO disk interfaces, anyone know
>anythng about an OWL Interface Disk Controler?  The board inside
>says LR Tech.  What interface is it and is it of any real use?

LR Tech is a SASI controller.  The slightly-newer Ken-Ton SCSI card is
supposedly compatible with the LR-Tech, so Ken-Ton software (SCSIsys,
Superdriver) should be able to use it.

As far as I could tell, the difference between LR-Tech SASI and actual
SCSI was that the LR-Tech didn't generate parity bits.

When I was running an LR Tech system, I was using the original
software for it, but then, I happened to have one of the supported
SASI-to-MFM controller boards around.

Willard
-- 
Willard Goosey  goosey at sdc.org