Trash to Treasure - Osbourne 1a Computer

 The Osbourne One is widely regarded as the first portable computer.  It was released in 1981, and although it didn't include a battery, it was advertized that it could fit under the seat of an airplane.  I have a soft spot for CP/M machines and so I've had the Osbourne 1 on my wish list for a couple of years.

Last year my friend Steve gave me a "fixer upper" Osbourne Executive.  That was an interesting machine, too, and this example was is really good cosmetic shape.  I spent quite a few hours restoring the machine, working on the CRT alignment, cleaning and lubricating the floppy disk drives, making boot media, and troubleshooting the main board.  But ultimately, I was not able to get it booting.  I isolated the fault to the main logic board, I think there is something wrong with the floppy disk controller because the machine can move the drive heads and step to tracks, but when it starts to boot, it reads in track zero, steps the head to the next track, then stops responding.  The machine behaves the same way with a Go-Tek drive emulator, so that's why I'm pretty sure the fault lies with the main logic board.  So I had put that repair on hold and was going to come back too it.

However, a more interesting option presented itself a couple of weeks ago.  I was shopping at Free Geek Twin Cities as I often do and they mentioned that an Osbourne had just come in.  It was in really rough shape, quite yellowed, and keys missing from the keyboard, but it appeared to be booting and asking for a boot floppy.  It wouldn't boot from the disk that had been left in the drive, but in my experience almost all of these drives from the early 80s need cleaning and lubrication before they can work correctly.  So, they offered me a good price on the Osbourne as a project machine and I purchased it...

The first order of business on a restoration like this was for me to get the machine booting.  I started by making some "known good" boot disks using my SuperCard Pro disk imaging setup.  I think I've covered this workflow before, but my current workflow for making boot disks for new to me machines is to find disk iamges on Dave Dunfield's site here.  I then use the fantastic tool HxE Floppy Emulator Software to convert the IMD disk image format to the SCP flux format used by my disk imaging hardware.  Then, I use the SuperCard Pro to write out the disks to hardware.

One hack that I've learned on the hardware side with these CP/M Machines is that since they must boot off Drive A it will have alot more wear and tear on it.  It makes sense to swap Drive A and Drive B as well as service both drives.  In this case, the drives mechanisms were from two different vendors but the control boards were the same.  The Osbourne 1 has power going to the floppy drive over the ribbon cables, this was not the case for the Osbourne Executive.  It turns out that all you need to do to tell which drive is the A drive is swap the termination resistor, there are no other jumpers on the drive controller board, after this the machine was booting!

Once I got the machine booting, it was time to swap over the external case parts from the Executive.  This article explains the differences between the very early Osbourne One computers and the 1a model that I have here.  I was quite fortunate to have purchased the 1a, not realizing at the time, but the case is exactly the same shape as the Osbourne Executive.  The front bezels are unique, so I cleaned up the front bezel of the Osbourne One with soapy water.  The Executive had a bulge under the handle in order to accommodate a fan, but many people feel the machine should have had a fan so I'm happy to have that as part of my Osbourne One even if it's a slight anachronism.

Another surprising item was that although the keyboards look identical and have the same connector they do not appear to be compatible with one another (I guess the analogy would be the XT and AT keyboards with the same connector but different scan codes). So, I removed all the yellowed keycaps from the Osbourne 1 computer and swapped the keyboard over into the Executive Housing.

The machine turned out lovely, I'm very happy with how it looks...

From the sides it is even more of a contrast as the old case was badly yellowed.

I'm glad to have the machine booting and running, but I would also like to add a Go-Tek with Flash-Floppy firmware.  I'm not quite sure how to do that with the non standard drive wiring on the Osbourne One, but that will be a project for another day.