[Coco] SCSI/SASI HD interfaces...

[Bruce W. Calkins]

More details on my Disto hard drive set up.

The 3-in-1 adapter provided a SASI pin out that went to a Adaptec -??4001 
card the same width and length as a 5.25" drive.  This drive had SASI cables 
on one end and MFM cables on the other for up to 2 MFM drives.  There are 
some addressing pins on the SASI end too.  I eventually got two spare cards 
and attempted to hook up a second set of two hard drives as the Disto 
documentation indicated was possible, however I did not have success at the 
time.  Later I got the book from Adaptec for the card and discovered that I 
need to cut a trace on one of the cards to get two cards to address properly 
together.  I moved about then and have not had the chance to attempt the 4 
hard drive setup again.  (It will need a GOOD power supply to power up those 
4 full height 8 platter, 16 head 5.25" drivers too.)

I have been tempted to break down the system as I have 4 of the Maxtor 
XT-2190 MFM hard drives and the asking prices listed on eBay have gotten my 
attention a time or two.  The drives were the largest MFM drives made and 
were popular with some early audio processing equipment.  Backing up those 
drives generally took 12 to 18 hours each for the 2 RGB-DOS partitions and 
DSAVEing the OS-9 partition.  The 768k Disto RAM disk pack did help smooth 
out the RGB-DOS backups.  It would have been a dream system in 1978, but I 
did not get most of it until after 1993.  Hopefully one of these days I'll 
find the right "Round-Tuit" and get that 1 megabyte + 768k CoCo 3 system 
running again.


Bruce W.

===================



----- Original Message ----- 

From: "Francis Swygert"

> Date: Fri, 3 Apr 2015 03:03:35 -0400
> From: Bill Pierce

>
> Both Kenton and LR Tech (Owl-Ware) were scsi hard drive systems and were 
> regularly advertised in Rainbow.
> ============================================
> I don't know the differences, but the Disto controllers were SASI and only 
> supported two devices, IIRC. They used less than 50 pins, but I think a 
> lot of the grounds were left out. IIRC SASI/SCSI used alternating grounds 
> (25 grounds, 25 signals). Disto may have dropped some of the signal pins 
> as well. Most of the SCSI controllers for the CoCo only supported hard 
> drives -- not much else was ever used on a CoCo, and it was quite the 
> unusual CoCo user that had more than two HDs connected -- most only had 
> one.
>
> Frank Swygert




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