Unix for 8080/Z80? [Re: WooHoo!! PC/XT Unix anyone?]

From: Gary Oliver <go_at_ao.com>
Date: Wed Jan 27 01:00:29 1999

At 11:30 PM 1/26/99 +0000, you wrote:
>> I actually have the hardware for the Winchester Disk System - it was the
>> controller I used to run my Big, Enormous, 27 Megabyte disk on my CP/M
>> system (SA4000 - 2 14inch platters! Big sucker.)
>And with a very complex headparking method.
>IIRC you had to put a clip into the head possitioner with the drive
>spinning at full speed to lock the heads. Then turn it off and put a
>screw through the drive pulley to lock the spindle. The problem comes
>when the clip and screw weren't stored with the drive....
>I'e heard stories of the motor start capacitor (it's a little AC
>induction motor) exploding and spaying oil over the rest of the machine.
>I don't particularly want to see this happen...

Sounds about right. However, I only lock the heads when I'm going
to trot it about. And I haven't done that for quite a few years.

Never had the capacitor problem, but I do fondly recall the damage
to my nervous system the time I brought it home and fired it up.
Of course, this was somewhat a "home brew" project. I bought the
drive, but there were NO S-100 controllers on the market at that
time. (This was about 1.5 years before Morrow came out with their
controller.) Being too stupid to know better, I designed my own,
hacked up, controller (bear in mind that I'm mostly a Programmer -
not a hardware weenie - though I've been messing with hardware
for a "few" years...)

Anyway, long story shortened: finished interface in a couple of
weeks, checked it out as best I could with offline tests. Built
power supplies for drive (needs 110vac control, and if I recall
correctly, 24vdc, 12vdc 5vdc and probably -12vdc - just about
everything and they have to be sequenced in the correct order
(or rather NOT in the INCORRECT order.)

Got everything up, dc-wise. Ready for drive. Powered up the AC
to the drive motor and damn near wet my pants. The most horrible
shreak and growl came from the drive. I've heard ("experienced")
a few head crashes in the my day and they usually kinda "sneak up"
on you - high-pitch squeal that gets louder and lower and louder and...
until there is no doubt what is happening. However, THIS drive just
started up screaching and howling.

I was about 10 feet from the drive when I powered it up, across the
room at the computer console watching my debug display for the
controller test. I don't think I've ever moved as fast as that
before - or since. Flew across the room to yank the power cord from
the wall - call it a reflex action - I wanted the damn thing OFF
quick - had the impression of my $4000 going up in smoke. (that's
what a "cheap" drive cost back then...)

Well, it turns out this SA4000 is DESIGNED to make that noise.
The starting torque of the motor is greater than the design for
the platters so the designers made a belt drive that was supposed
to SLIP for a few seconds. Imagine your power-steering belt on
your car when it's cold and the belt is a little loose. Same
effect, though I never experienced that on a disk drive

Anyway, drive worked, controller (eventually) worked, but Morrow's
was MUCH better so replaced it eventually. Drive worked fine
for more than seven years before I retired it to the garage
"pasture." Still worked the last time I fired it up.

For those not able to picture the size of this drive: 14 inch
platters, with cast aluminum base in a box about 10 inches
high by 26 inches deep by 19 inches wide. If this size box were
filled with current run 4gbyte drives, it would contain at least
750 gbytes and probably need about the same amount of power.
A density factor of about 27000:1. Not bad for 15 years.


Received on Wed Jan 27 1999 - 01:00:29 GMT

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