Creating new CP/M disks - Progress on IMSAI

M H Stein dm561 at
Sat Jan 12 11:53:13 CST 2008

Date: Sat, 12 Jan 2008 09:23:02 -0500
From: "Richard A. Cini" <rcini at>
Subject: Re: Creating new CP/M disks - Progress on IMSAI

>> As a matter of fact, the motor did run constantly on many 8" drives (remember
>> that many had 110V AC motors).
>> m

>Yes, but the heads engaged and disengaged to reduce wear. On modern drives,
>the heads remain engaged but the motor stops.

Exactly; that's why you're having problems. But A & A seem to think there's
something wrong with /MOTOR ON being on constantly, which can be quite 
normal on an 8" FDC. Some FDCs do have an option to latch it ON with pin 16 
and turn it OFF with pin 4 BTW.


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