View Full Version : Osborne 1 drives will read but not write.

November 28th, 2009, 11:53 PM
Hi. I am new to this forum. :D
I recently found an Osborne 1 at my work, and I have been working to bring it fully back to life. Tezza has helped me a lot already. The good news is that it is in physically good nick, boots CP/M and can run SuperCalc and Wordstar (the apps I tried so far). Two of the paper filter capacitors in the power unit have exploded, but I have been replacing those, no problems.

The next bug I found is perhaps a but more tricky, and I thought it was a good time to introduce myself here and throw the problem out amongst the gurus.

First I found the Osborne will not format disks. Both drives A and B behave the same. I can hear the disk spinning but no head movement. The COPY program hangs as it begins to format the disk.

To see if it was a general problem with writing I tried saving a spreadsheet from SuperCalc onto the same SuperCalc floppy. I got the error "BDOS err on B: Bad Sector". I think this is just as likely to be a problem with the Osborne as with the disk.

Any tips on the best way to begin debugging this issue?

November 29th, 2009, 10:25 AM
If you can write to already-formatted disks, then the most likely culprit is the INDEX/ signal from the drive not making it to the controller. The WRITE TRACK command of the WD17xx waits for an index pulse before it begins formatting; without said pulse, it will wait forever.

This should be pretty easy to run down with a logic proble.

November 29th, 2009, 11:34 PM
Thanks Chuck. You have a very detailed knowledge of these machines!
In fact the answer may (hopefully) turn out to be very simple, even potentially embarrassing. Tezza had a brainwave, and I think he might be right. The thing about people like me who haven't used 5" floppies for 20 years, is that we might forget a few basics :blush:. Tezza asked if I took the write protection tape off the floppy. Good question! Nope. haha A potential cause.

But I won't be able to confirm this for a few days because I have another blown capacitor (the last paper filter one) to replace, and I have a business trip tomorrow.

But if that is the case, the error message surprises me. A bad sector error when the write-protection tape is on and saving from SuperCalc!? And the format program just hangs? Is that right Chuck?

November 30th, 2009, 12:33 AM
Hi Richard,

I'm no CP/M guru but by coincidence I did read the below just a few minutes ago when I was browsing through Infoworld in Goggle books. I came across an article called "CP/M Eludes Home Market" in Infoworld, 11th June, pages 46-47. In the article it says...

"Digital Research has been criticized for CP/M's lack of documentation and its cryptic error messages — like "BDOS ERROR ON B:"

Maybe that says it all :)

It's good news though because I strongly suspect the problem was a read-only tab covering the write slot, and once your get the PS caps replaced you'll find you have a fully working Osborne 1. I'm almost tempted to drag out my own Osborne again to see if I can reproduce the exact error by write protecting a blank disk and trying to format it. However, other more knowledgable folk than me should be able to confirm the likelyhood of this being the issue.


November 30th, 2009, 12:54 AM
Haha yeah. It turns out that there is a lot to learn about CP/M for me.

You know, if it turns out that the only true faults for this Osborne were a few blown caps then I will feel I got off really light! Vintage computing is not supposed to be that easy, right? That would mean that before I put power through it, it was a fully functioning machine. Fingers crossed.

November 30th, 2009, 08:40 AM
But if that is the case, the error message surprises me. A bad sector error when the write-protection tape is on and saving from SuperCalc!? And the format program just hangs? Is that right Chuck?

That shouldn't be the case. If the BIOS is doing things right, CP/M should return a "BDOS Error on A: - R/O" error. But one never knows exactly what the BIOS implementers decided to do.

Should you ever get a system with 8" drives, remember that the tab works the opposite way--you need it to enable writing on the floppy. This confused a lot of people who initially made the change from 8" to 5.25".

Personally, I like the 8" system better--you need to do something in order to write on a floppy. Sort of like 1/2" mag tape--"no ring, no write".

November 30th, 2009, 10:34 AM
So the plot thickens! Well, we will see, probably on Friday.

November 30th, 2009, 11:26 PM
Ok, I couldn't resist it.

I dragged the old Osborne back onto the bench, booted up, put a write protected disk in the B drive and tried the same things Richard had attempted with the following results.

Using Format from the Osborne COPY utility:
- Display stuck on track zero. Drive just spun and spun and spun. I let it go for about 2 mins

Using Copy from the Osbone COPY utility:
- Copied first 5 tracks from A:, then display sat on track zero of B and the B drive just spun and spun and spun. As before I let it go for what seemed like ages but probably was 2-3 mins

Saving a file on drive B from Supercalc
- Bdos Err on B: Bad Sector

Seems the Osborne BIOS implementers didn't follow the rules :)

Actually that's one of the things that used to bemuse me about CP/M in the day. You had all kinds of manufacturers claiming CP/M was a "standard" and CP/M compatibility was important. However, the truth was almost every CP/M implementation was slightly different and the disk formats were usually different. A CP/M disk written in one manufacturer's computer often couldn't be read in another. Compatibility appears to have been a myth, although this didn't stop the market desiring CP/M implementation even though software for that particular implementation might not have been plentiful.


December 1st, 2009, 12:28 AM
That's great data Terry. Thank you. And that is good news! Those are the same results I got. Hopefully that means there is nothing wrong with my drives. I am really looking forward to (hopefully) getting back to Osborne business now!

Yeah, I got the same impression reading the Double Density manual. The Osborne supports about 5 different disk formats, and the first page of the manual is a polemic complaining about the lack of standards in the industry. That manual was interesting that way actually. You would never see a computer manual written like that today. Casual comments like "those familiar with assembly will of course be able to program the drive to do many things." Well, Indeed! Like Linus Torvalds said: "Do you miss the old days when men were men, and wrote their own device drivers?" haha

December 1st, 2009, 09:24 AM
Actually that's one of the things that used to bemuse me about CP/M in the day. You had all kinds of manufacturers claiming CP/M was a "standard" and CP/M compatibility was important.

Consider the world before CP/M. Everyone had a different, mutually-incompatible operating system. It wasn't unusual for a manufacturer to sell mutually-incompatible hardware and software platforms. Portable Unix, in 1972 was still largely a dream.

When CP/M began to be offered to OEMs, most were suspicious. One aspect was the generally-accepted idea that one should endeavor to "lock a customer in"; that is, to make it difficult to switch platforms. This ensured that said customer would be motivated to keep buying your products.

The real credit that should go to Gary Kildall is that he recognized that with microprocessors, the game had changed--the world was about to be flooded with computers all using the same instruction set. Intel, for example, would never package or license ISIS to be sold with other vendors' hardware, which is why you don't hear much about it.

As far as media formats go, Kildall considered the single-sided, single-density 8 inch IBM 3740-formatted floppy to the standard interchange medium. If you obtained an OEM license for any of his 8-bit products, that's what you got. If it was an operating system, you could be assured of being able to boot it on an Intel MDS. This policy lasted well into the 1980s.

Even Microsoft followed much the same model early on. OEMs could create their own I/O subsystem to go with Microsoft's MS-DOS. That's why, for example, there are two files that are loaded when DOS is booted (IO.SYS and MSDOS.SYS--or IBMBIO.COM and IBMDOS.COM).

For the time and the limited and varied hardware, CP/M was revolutionary, if not technically sophisticated.

December 3rd, 2009, 08:36 PM
Well, good news today. I soldered in the new PSU capacitor, put her back together and tried the writing operations again -- this time with the write-protect tape removed!

Formatting a disk - Fine
Sysgen - Fine
COPY of CP/M disk - fine
Saving a spreadsheet - fine

Back to no known problems, which is nice. Time to play.

December 4th, 2009, 02:31 AM
Good news!