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From: blochowi@rt1.cs.wisc.edu (Jason Blochowiak)
Newsgroups: comp.sys.apple
Subject: Re: GS-Disk II compatibility
Message-ID: <4073@puff.cs.wisc.edu>
Date: 15 Dec 89 22:08:35 GMT
References: <8912132032.AC00027@adam.DG.COM> <4366@hydra.gatech.EDU>
Sender: news@puff.cs.wisc.edu
Reply-To: blochowi@rt1.cs.wisc.edu (Jason Blochowiak)
Organization: U of Wisconsin CS Dept
Lines: 27

In article <4366@hydra.gatech.EDU> ccastbs@prism.gatech.EDU (Shannon Bell) writes:
>Does anyone know why a disk II controller with two drives will work
>perfectly in slot 6 of a GS but not in slots 1 or 2?
> [Deleted mention of read errors]
>Is there something special about the slot 1/2 architecture, relative to
>the slot 6 architecture, that would prevent the proper functioning of 
>a Disk II contoller?

	Well, the //gs runs faster (~1.5Mhz faster) than the other Apple //'s,
so Apple had to do some relatively strange stuff to get the disk drives (which
use timing dependent software) to work properly. Basically what happens
is: when the //gs sees software turn the drive motor on, it slows the machine
down to 1Mhz (the "standard" // speed) so that the timing works correctly, and
speeds it back up when the motor gets turned off.  For various reasons, this
automatic slowdown is only available in slots 5-7, so when you put the
controller card in slot 2, the //gs tries to run the software at full blast,
which doesn't work out right - I think (not at all sure on this one) that if
you set the system speed to "Normal" (in the Control Panel) the card will work
in slot 1 or 2.

>Shannon Bell
>Internet: ccastbs@prism.gatech.edu


--
      Jason Blochowiak - blochowi@garfield.cs.wisc.edu or jason@madnix.uucp
       "Education, like neurosis, begins at home." - Milton R. Sapirstein