6 Jul
2000
6 Jul
'00
2:05 p.m.
What you say seems to wash with what I've seen even on later model drives,
Tony, but my main concern is that several of the jumper options on later
(after 1981) 8" drives used pin 2 for various options having to do with
overlapping seeks between two or more drives, radial head-loads, and things
like that. Shugart drives and Siemens drives all seem to direct the user to
Pin 2 for such options, but they all seem to have on-board track counters
for their write current control logic. It's likely the Qume's have, too,
since they're called out in one of my standalone FDC/FDD boxes as an option,
and I know them to use those options via Pin 2.
Hooking it up is necessary, but not sufficient in such cases as I've
mentioned, to ensure that the signal gets through. Careful examination is
called for in this case.
Dick
----- Original Message -----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Thursday, July 06, 2000 5:30 PM
Subject: Re: Tim's own version of the Catweasel/Compaticard/whatever
use
>
> My point here was that the important effect downstream of the controller
is
> that write current is reduced in some cases.
Most post 1980 drives kept
> track of the track on which the heads were sitting and didn't use the
signal
on Pin 2.
I'm glad that SOMEONE caught that!
I guess I'm used to the older 8" drives, because just about all of mine
the Reduce Write Current (RWC) signal on pin 2. The
only exception I can
think of is the Elcomatics I have on my PC/XT. Those have a second
slotted optoswitch on the head positioner which is set to operate at
cylinder 43 and all higher cylinders. It's a jumper-selectable option
whether this, or pin 2, is used for RWC.
<snip>
-tony
Dick