[Coco] Another 'rare' opportunity on eBay

[Bruce W. Calkins]

RGB-DOS provides for 4 hard drives useing the Disto hard drive adapter. 
That requires two Adaptec SCSI to MFM converter boards, with two drives each 
AND a little known trace cut on one Adaptec board.  Disto's floppy drive 
controllers and the RAMdisk used a Mini-Expansion Buss that the hard drive 
adapters converted to a modified SASI pinout.  The Cable spreads the control 
and data signals our to the ends of the SASI buss.  The middle lines in the 
SASI buss were for future expansion.

As to the Tandy hard drive "adapter", It does not have a ROM.  Therefore it 
must use the software in the drive's controller and software in the computer

Bruce W.

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----- Original Message ----- 
From: "Frank Swygert"


> The Disto HD controllers were also SASI, that's why they didn't work with 
> more than one drive as far as I recall. SASI is a subset of SCSI I 
> believe -- or rather SCSI is a more robust and useful SASI (SASI came 
> first). The Disto controllers MIGHT have worked with two drives, but I 
> distinctly remember from a manual of the one I had and from Tony himself 
> that it was really a modified SASI controller, at least the little board 
> that fit inside the Disto floppy controller. I recall a special cable had 
> to be made for it to, or one purchased from Tony. That was mostly because 
> the controller used a pin header on the controller end though.
>
> It should be possible to use that old Tandy controller with a standard 
> SCSI drive (old original SCSI). As someone stated, however, the ROM inside 
> was limited to a few Tandy specific drives, you can't change the drive 
> specs. That might not mean you can't connect a 100MB SCSI drive and use 
> 15MB of it though.... The old Tandy hard drives were small by todays's 
> standards! I remember when a 20MB (that's right, MEGABYTE, not GIGABYTE!) 
> was a healthy drive. Still is for a CoCo...
>
> -----------
> Frank Swygert