OK, I kept digging, and I finally came across my AtariST/Amiga switchable
mouse - so I might have an Amiga soon.
(I still didn't find my ratzenfrackenfrippenfrumble eprom burner w/builtin
eraser - so I'm considering buying a separate eraser just to have a spare.)
With all this talk of "Operating Systems you're not supposed to run on your
computer" lately, this just begs the question: I *thought* there were
versions of OS-9 that existed for the AtariST and/or the Amiga - as in
OS-9/68K. Anybody know anything about a possible Amiga version? I'd be kind
of interested in running that, just because I'm not supposed to... ;-)
Laterz,
"Merch"
--
Roger "Merch" Merchberger -- SysAdmin, Iceberg Computers
_??_ zmerch at 30below.com
(?||?) If at first you don't succeed, nuclear warhead
_)(_ disarmament should *not* be your first career choice.
Randy McLaughlin <cctalk at randy482.com> wrote:
> I am 99.99% sure it changes the RPM, I have some TEAC 1.2's laying around
> I'll plug one in and ground pin 2 to check it.
>
> For the TEAC it is enabled via an option jumper, default is to ignore it.
Changing the RPM is an option on SOME drives, and for PeeCees to work it
must be OFF. It is very useful for Classic Computers, though.
The high density select signal (pin 2) may or may not switch RPM, but it
always switches the write current. Writing on HD media with DD write current
will produce no effect (the field is too weak to affect the media), while
writing on DD media with HD write current will magnetise the media so
strongly that it'll be impossible to rewrite and unusable until you
bulk-erase it. So pin 2 MUST always select the correct write current for
the media type.
3.5" drives use the media type hole instead to select the correct write
current. Those who punch or cover that hole to magically "change" the
media type get what they deserve.
MS
>From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
>
>On Thu, 2005-03-10 at 17:18 -0800, Steven Canning wrote:
>> Jules,
>>
>> I proposed doing exactly that (i.e. passing "raw" floppy data through a
>> parallel port) last year along with some simple math that showed it could be
>> done.
>
>Yep, I hadn't forgotten :-) (I made sure I kept all the relevant
>messages too)
>
>Wasn't the problem that the parallel port just doesn't have the raw
>speed for it to work for all disks though? At which point buffering
>becomes necessary, which was also the point that everyone went quiet on
>the subject :-)
>
>With the cable you mention, how are you supposed to get the created disk
>image back onto a disk again? (Personally I need to be able to restore
>data from an image back to a floppy)
>
>I need to do some reading up on what the floppy drive's write gate
>signal does. If spitting data from an image down the 'write' signal wire
>at the same speed as it was read is good enough (and 'write gate' is
>actually a 'R/-W' signal) then maybe it isn't too complex. However if
>write gate is actually dependant on the data stream too (needing it to
>be understood) then it could be rather tricky.
Hi
There are two write signals. One is write data and the other
is the write gate. The write gate is like a write enable. It
also turns on the erase signal the cleans the edges of the track
that is being erased and over written.
The drive has nothing to set the timing of the signals coming
to it. You can not just directly use the recorded data without
realigning the clock edges. This includes the possibility of
write compensation as well.
There are rules about when you use the compensation. It helps to
understand a little about digital recording. The write signal
just makes a bunch of static +- signal levels on the disk. When
played back, the head only sees the transitions and not the levels.
This means that the effective edge of the transition is what is
important. When the signals are on the surface of the disk,
they are a bunch of magnetic fields. They interact in such a way
that there is an averaging or frequency loss if too many transitions
are close together. Compensation helps to avoid this. It is
best to put some compensation in both the receive an transmit
ends. It is simpler is to just use it in the transmit ( or write )
circuit. This is what is done for writing higher density floppies.
If you record all the info played back, you need to realign
the timing and possibly add compensation. It is not an impossible
task but does require some knowledge of the particular technology
used for that floppy format.
You also don't need to know what the data is, just what the
rules are for placing levels on the disk. It is even conceivable
that one can do a better job than the original controller did.
One can do some test signals on that particular media and
determine just how much compensation works best on each track!
Like the 6 million dollar man, "we can rebuild you better than
before".
Dwight
>
>Note that personally I *don't* need to understand the image on the host
>machine (at this stage) - all I care about is backing up floppies to
>modern hard disk and being able to recreate them again. Understanding
>via software decoding might be nice one day, but in the shorter term my
>concern's with all the thousands of disks we have at the museum with
>data on that are likely decaying...
>
>cheers
>
>Jules
>
>
>
Randy McLaughlin <cctalk at randy482.com> wrote:
> Pin 2 on a 34 pin floppy connector is a little used pin. It was used to
> change the RPM on some 5.25" 1.2mb drives.
>
> It changed the RPM from 360 RPM (pin 2 high) to 300 RPM (pin 2 low). This
> was supposed to make it easier to read/write DD disks in a HD drive.
>
> Only early AT controllers needed it, later controllers kept this pin high
> and used an odd transfer rate.
Hmm, my understanding is that pin 2 is LOW when the odd 300 kbit/s transfer
rate is used, and all HD drives use this pin to switch the write current
to produce the 300 Oersted field necessary for DD media or the 600 Oersted
field necessary for HD media.
MS
Mark Wickens <m.wickens at rhodium-consulting.com> wrote:
> How many tapes does the software occupy,
1
> and what format do they need to be written in?
Physical tape record level images are on my FTP site, just write them to
the tape. Treat it as a foreign tape whose format you don't know or need
to know.
(The "don't need to know" part refers to those merely *writing* tapes.
If you do want to know the format, you are more than welcome to, and it's
described in the documentation, specifically in "Installing and Operating
4.3BSD-Quasijarus UNIX on the VAX".)
MS
Any takers? I will pre-pay for shipping and media if anyone on the list
can help me out with writing it with 4.3BSD Quasijarus0c.
Thanks in advance,
John Willis
----------
From: msokolov at ivan.Harhan.ORG (Michael Sokolov)
Date: Fri, 11 Mar 05 09:12:14 GMT
To: willisjo at zianet.com
Subject: Re: Quasijarus Media
John Willis <willisjo at zianet.com> wrote:
> We had previously discussed my interest in getting some install media for
> Quasijarus. I finally have my MicroVAX II running with a working TK50 drive.
> Are you still offering the media kits for a fee?
I would be if I had my TK50 writing setup working... It isn't at the
moment :-(
I really want to start providing real tapes like UC Berkeley did, but I'm
so swamped that I cannot tell when, if ever, will I get myself set up to
be able to do it. Until then you should ask on ClassicCmp if anyone can
write you a tape from the images on my FTP site. I'm sure there are plenty
of people there with the necessary setup who'll do it for you. When you
post your request to the list, feel free to mention that you've asked me
and that I lack the necessary hardware setup at the moment.
MS
if you are targeting 5.5us, then it is a 220pf cap. The formula for the pulse width for a 121 is 0.7 * R * C, where 220pf is 220 X 10-12 and R is 25000 then the time comes out to 5.5us. I think the "l" was just a mistype.
-----Original Message-----
From: Bill Sudbrink <wh.sudbrink at verizon.net>
Sent: Mar 11, 2005 7:14 AM
To: cctalk at classiccmp.org
Subject: Name that cap...
to jump out at me. Part of the accompanying text says: "The RC time
constant
is adjusted to give an output pulse width on pin#1 of the 74LS121 of 5.5
ls."
I assume "ls" is an oddball abbreviation for microsecond?
Actually, I know someone with the capabilities of doing this, but I don't
know if he has the time.
Let me ping him and see what he thinks.
-----Original Message-----
From: cctech-bounces at classiccmp.org
[mailto:cctech-bounces at classiccmp.org]On Behalf Of Jules Richardson
Sent: Thursday, March 10, 2005 8:26 PM
To: cctalk at classiccmp.org
Subject: Re: USB Universal Floppy Disk controller
On Thu, 2005-03-10 at 19:49 -0500, Barry Watzman wrote:
> What we need so badly is a USB universal floppy disk controller.
Personally I'd rather have parallel or serial or SCSI interfaces, but
each to their own :-)
But yep, agreed. I certainly need *something* that can archive / restore
classic formats to/from modern(-ish!) media.
> Can't anyone design one? It's way over my head
Over mine too really. I'd be able to build one given a schematic, but
probably couldn't design something from scratch.
Actually, I'd much prefer a schematic anyway for peace of mind as well
as curiousity value.
Given the know-how on the list I'm suprised there hasn't been a
collective effort in the past to build something.
Maybe the majority of us either:
1) only specialise in one machine and so do backups in whatever way's
easiest for our own hardware,
2) are lucky enough to be blessed with online archives of software so
backups aren't needed
3) aren't taking any backups at all! :-)
cheers
Jules
