bryce@hoser.berkeley.edu (Bryce Nesbitt) (09/11/87)
[ Cross-posted to sci.electronics because it's about electronics,
though the problem showed up with the Amiga Computer. Please edit the
group line if your response is not approprate to both groups. ]
[ You need to know that the 90mm disk drives of the Amiga Personal Computer
make a clicking noise when empty. You also need to know that 90mm ~=
3.5 inches ]
Recently I posted a Kickstart patch to turn 1.2 Kickstart into 1.2
noKLICKstart. I know it was popular because hundreds of people
responeded (Email and otherwise). Sadly, many of those
complained that it did not stop the click of *their* drives. What
follows is a technical desciption of what goes on and how to fix
it:
Seems that Amy has been "sleeping around" with a lot of different drive
manufacturers. No offical word, but my spies report:
Mitsumi
Matshshita
Sony
NEC
Chinon (Amiga 500)
Panasonic
Which reads as a "whos who" of 90mm drive manufactures.
The reason for the clicking in the first place is to detect disk insertion.
The drives all have a /CHANGE signal, which is latched LOW when a disk is
removed. This must be a latch, or you would run the possibility of missing
a disk change. To see if a new disk is in, you must RESET the latch. This,
for reasons byond my comprehension, is done with the /STEP signal. (BTW:
I know the reasons, I just don't agree.)
So now you know why the drives click. To prevent it I patched Kickstart
to continutally step OUTWARD instead of forth and back. When the head
reaches the track zero sensor the drive says "hey", "you can't go that
way". It resets the /CHANGE latch, but does not step or click. Saves
wear and tear on the drives, is silent, and is generally a good idea.
"But no" said some manufacturers. The drives that don't like this are a bit
dim... you try to step the head past zero and they simply let you bash
the head into the stop. No noise or wear and tear savings here! These
drives all have ample circutry to do it the first way... they just don't.
Drives that are know to work include----
Sony
NEC
Chinon (Used in the Amiga 500, single +5 supply, very low power)
Panasonic
Drives that don't----
Matshushita
Mitsumi
Drives that I have received a conflicting report on----
Panasonic (one person says it's the same as Matsushita... unconfirmed)
Drives that are not used in the Amiga, but won't work anyway----
Fujitsu
SOME drives provide an alternate /CHANGE reset signal, often on Pin 1. But
all the drives that do, *already work fine*. If you want to get a non
working drive to work you would need to either:
A> Cut /STEP on the drive PCB so it gets to the latch, but not the stepper
motor. Now add a gate that will disallow /STEP if the track zero sensor
is active and the direction is out.
B> Tap the change sensor on the board and drag it external. Use /STEP to
reset your external latch (ignore the internal one). Now add the circuit
to disable /STEP when track zero is active and the direction is out.
Both are simple, but painful to do. I don't expect that anyone will try
them.
There seem to be no *real* standards in 90mm drives. Every manufacturer
is a little different. The /CHANGE signal is the most volitaile of all.
The definitions of Pins 1,2 and 34 are wildly different from manufacturer
to manufacturer. Such is life...
|\ /| . Ack! (NAK, EOT, SOH)
{O o} .
(") bryce@hoser.berkeley.EDU -or- ucbvax!hoser!bryce
U jdow@gryphon.CTS.COM (Joanne Dow) (09/15/87)
In article <3688@zen.berkeley.edu> bryce@hoser.berkeley.edu (Bryce Nesbitt) writes: >[ Cross-posted to sci.electronics because it's about electronics, > though the problem showed up with the Amiga Computer. Please edit the > group line if your response is not approprate to both groups. ] >[ You need to know that the 90mm disk drives of the Amiga Personal Computer > make a clicking noise when empty. You also need to know that 90mm ~= > 3.5 inches ] > >Recently I posted a Kickstart patch to turn 1.2 Kickstart into 1.2 >noKLICKstart. I know it was popular because hundreds of people >responeded (Email and otherwise). Sadly, many of those >complained that it did not stop the click of *their* drives. What >follows is a technical desciption of what goes on and how to fix >it: >all the drives that do, *already work fine*. If you want to get a non >working drive to work you would need to either: > >A> Cut /STEP on the drive PCB so it gets to the latch, but not the stepper >motor. Now add a gate that will disallow /STEP if the track zero sensor >is active and the direction is out. > >B> Tap the change sensor on the board and drag it external. Use /STEP to >reset your external latch (ignore the internal one). Now add the circuit >to disable /STEP when track zero is active and the direction is out. > >Both are simple, but painful to do. I don't expect that anyone will try >them. > Er, there may well be a better way. If you're going to hack at the drive why not tell the fool thing to not step the head unless the head is loaded? The clicks come with the head unloaded. Hence going in and adding a gate to intercept the head step pulses unless the head is loaded should do the trick admirably. Hm, maybe my hardware background is showing here... SW weenies shouldn't know this kinda stuff, nie? <^_-> -- <@_@> BIX:jdow INTERNET:jdow@gryphon.CTS.COM UUCP:{akgua, hplabs!hp-sdd, sdcsvax, ihnp4, nosc}!crash!gryphon!jdow Remember - A bird in the hand often leaves a sticky deposit. Perhaps it was better you left it in the bush with the other one.
wtm@neoucom.UUCP (09/18/87)
In my engineering tunure, I've discovered disk drive interfaces are nearly as frustrating as RS-232 (and other) serial ports :-). A wihile back I was trying to tame a cantankerous Teac 55-B drive in an AT&T 6300. I called Teac to get the low-down on the drive. When I got through to their engineer he asked "What have you got", to which I said "55-B". He said, "like I said, what have you got". It turns out that there were something like 95 OEM versions of the 55-B. Their engineer further expalained that on average, the layout of the PCB for the "generic" models of the 55-B changes about every two weeks (!). The upshot of this is that drives you get on the surplus market can be almost anything at all. In the case of Teac, they disavow all knowledge of any of the OEM versions. Thus, buyer beware when adding surplus drives to your system. Pins 1, 2, and 34 as Bryce noted can be almost anything. At least defacto standardization has taken over for most of the rest of the interface. For the moment, I'll stick with my engineering solution of leaving something in the drive. Bill wtm@neoucom.UUCP <<disclaim this article at your own risk>>
grr@cbmvax.UUCP (George Robbins) (09/29/87)
In article <3688@zen.berkeley.edu> bryce@hoser.berkeley.edu (Bryce Nesbitt) writes: > > Seems that Amy has been "sleeping around" with a lot of different drive > manufacturers. No offical word, but my spies report: > > Mitsumi > Matshshita > Sony > NEC > Chinon (Amiga 500) > Panasonic > > Which reads as a "whos who" of 90mm drive manufactures. > I think the "official vendors are NEC, Matsushita and Newtronics for the A1000, Chinon for the A500 and A2000. The Chinon drives aren't 5 volt only, although a number of drives tentativly approved for the A500 are. > There seem to be no *real* standards in 90mm drives. Every manufacturer > is a little different. The /CHANGE signal is the most volitaile of all. > The definitions of Pins 1,2 and 34 are wildly different from manufacturer > to manufacturer. Such is life... No hard and fast standards, when you order a few tens of thousands, you just tell them what options you want and send the money. This track zero thing has never been a requirement, since the software normally takes care of the problem. -- George Robbins - now working for, uucp: {ihnp4|rutgers|allegra}!cbmvax!grr but no way officially representing arpa: out to lunch... Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)