Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!cornell!uw-beaver!tikal!dad!nelson
From: nelson@dad.UUCP (Paul Nelson)
Newsgroups: comp.sys.apple
Subject: Re: D-I-Y SCSI for Apple ][
Message-ID: <3606@dad.UUCP>
Date: 12 Sep 88 18:15:58 GMT
References: <7841@mtune.ATT.COM>
Distribution: na
Organization: R & D Associates, Tacoma, WA
Lines: 38

in article <7841@mtune.ATT.COM>, rkh@mtune.ATT.COM (Robert Halloran) says:
> 
> Has anyone tried 'rolling their own' SCSI hard disks for an Apple ][?
> I'm debating whether to buy an already-packaged drive vs. a 'bare' SCSI 
> drive and power supply for my GS.  What drives/controllers/software were 
> used?  What (if any) major problems were encountered?  
> 
I own a CMS 60M hard drive with a CMS scsi interface.  After reading
alot about building your own scsi hard drive, I opened up my CMS drive
to look inside.  I was quite suprised to find that it contained only a
power supply, a seagate st277N ( i'm not sure of the exact model number), and
a small pc board cable adapter to convert the seagate's 50 pin ribbon to the
25 pin apple type scsi cables.  the seagate drive has a built-in scsi 
interface and has only the 50 pin scsi i/f cable, a small cable that is 
wired to jumpers for address selection, and a cable for power. 

The hard drive itself would not be hard to make.  You could probably buy
the parts for around $600.  The problem is with the scsi i/f card for the
computer end.  You can buy one from CMS for under $200 ( i think,  i haven't
asked a dealer, but my CMS hard drive was packaged for a Mac and the scsi
i/f card came from another package somehow... the dealer did the dirty work)
The real question is this:  I would like to have Apple's scsi card, but I
don't think that I could use it with a 60M drive, since it would want to
access the disk as one volumn (i'm assuming this).  Since Prodos won't deal
with a volumn that big, I would loose half the disk.  The CMS i/f card makes
the 60M drive look like two 30M drives to Prodos, so you can access the
whole disk.

I would like to get some more info on how the apple scsi card talks to 
disks:
	what is the largest disk size?
	how does it find the disk (how do you tell it that address xx is a disk)?
	Could I write my own drivers for accessing scsi disk drives or any other
	 scsi device?
If anyone with an apple scsi knows the scoop, please let me know.

								Paul Nelson
								...tikal!dad!nelson