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Re: help writing bootable Osborne disks from stream files

Posted: Sat Jul 17, 2021 2:18 pm
by KennyPowers
brightcaster wrote: Fri Jul 16, 2021 9:05 pm Please boot from drive B and use the COPYSYS command to write a copy of the boot floppy on drive A. Does the floppy written on A this way look the same on the odd tracks?

David
Here's what I did:
  1. Wrote two system disks from the stream files you posted on the first page.
  2. Booted the Osborne from drive B using one of those disks.
  3. Put the other disk in drive A and used COPYSYS to write a system disk with drive A
Findings:
  1. The system disk written by drive A will boot the Osborne from either drive A or B.
  2. The system disk written from the attached stream files using my 40-track TEAC is still only readable by the Osborne's drive B.
  3. I then used COPYSYS to write a system disk with the Osborne's drive B. That disk will boot the Osborne from either drive A or B.
Am I right in thinking that if drive A and B were aligned differently, then niether (a) or (c) above would have worked?

I've linked to the stream files for the system disk written by the Osborne's drive A, dumped by both a 40-track and 80-track drive. That disk has been rewritten a lot, just FYI, and I don't have a bulk-eraser.

https://www.dropbox.com/s/kbaestigdzp4r ... p.zip?dl=0
https://www.dropbox.com/s/3131lmbxsuhuv ... p.zip?dl=0

Re: help writing bootable Osborne disks from stream files

Posted: Sat Jul 17, 2021 3:48 pm
by brightcaster
Okay it's not a problem of tracking but a matter of bitcell lenght!

First you have to know that the COPYSYS command does not format the whole floppy but only writes some system files to it. So some parts are written by drive A and other parts are written by your TEAC drive.

If we look to sectors written by drive A we see that the bands in the scatter view are no longer exactly at 4, 6, and 8µs but around 3.9, 5.7 and 7.5! That's about 7% off specification! The sectors written by drive A are shorter and the gaps are wider than those written from the streams by your TEAC drive!

On the other hand drive A sees correctly written bitcells as beeing 7% to long and its decoding may go wrong sometimes resulting in read errors. I'm sure that the decoder will allow some difference but 7% could be to much for your drive A.

I will add some pictures, stay tuned...

David

Re: help writing bootable Osborne disks from stream files

Posted: Sat Jul 17, 2021 4:15 pm
by brightcaster
The tracks written by your A drive are the ones marked with the yellow H (modified). If you will look at them yourself you can move the cursor on a block and see the results in the scatter view. (compare yellow vs green to see the difference).
Photo1.jpg
Next is the analyzer view of the HxC tool which shows the difference in the sector length written by the A drive.
Photo2.jpg
David

Re: help writing bootable Osborne disks from stream files

Posted: Sat Jul 17, 2021 4:18 pm
by brightcaster
This is a track written by the TEAC, where the bands are quite flat with proper timing.
Photo3.jpg
And this is what drive A does when writing the sectors (the gaps are still written by the TEAC with proper timing)
Photo4.jpg
David

Re: help writing bootable Osborne disks from stream files

Posted: Sun Jul 18, 2021 12:08 am
by SomeGuy
So in other words, it sounds like a drive speed issue. Check and adjust the A drive's RPM speed. Check for any damaged motor control components.

Re: help writing bootable Osborne disks from stream files

Posted: Sun Jul 18, 2021 3:36 pm
by brightcaster
The procedure is described in the manual at page 217 (8.3.2) and the "Osborne Disk Exerciser Programm" should be on one of the system disks. But you need a special alignment floppy!

http://www.bitsavers.org/pdf/osborne/2F ... n_1983.pdf

On the other hand there is a strobe wheel on the drive which will be second choice but still much better than 7% off specification! (Procedure is also described in the manual.)

David

Re: help writing bootable Osborne disks from stream files

Posted: Sun Jul 18, 2021 9:25 pm
by KennyPowers
Thanks a ton guys! I know the topic strayed a bit from anything KryoFlux related. I'll be traveling for about a week, but I'll open the Osborne up when I get back and see if I can't get drive A "up to speed" so to speak :lol: It's a shame that those alignment diskettes are so hard to find now. That sounds way easier than using the strobe wheel. Do modern household LED bulbs still flicker at 60Hz in the US, or am I going to have to hunt down an old incandescent bulb? :lol:

I'll leave you with a before-and-after of the one I've cleaned up, re-capped, etc vs its sibling that I haven't touched yet. They both looked the same when I got them. I'm told the other one has some 3rd-party upgrades that will become immediately obvious when taking it apart. And after these, I have a room full of old Apple stuff to play with...

Image

Re: help writing bootable Osborne disks from stream files

Posted: Mon Jul 19, 2021 8:33 am
by brightcaster
Some LED lamps still do flicker. I tested it on my vinyl player. The rule is: the cheaper the better ;-)

David