Cracking open the Osborne 1: The original portable computer
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A classic luggable PC
A classic luggable PC
The Osborne 1 was the word’s first self-contained portable personal computer. Many of the design decisions and innovations first seen in the Osborne 1 are still being used today some 25-plus years later. We could not resist taking a look inside this piece of computing history in this TechRepublic Cracking Open Photo Gallery.
A quick note on the Cracking Open Photo Galleries: I am not an engineer and these galleries are not attempts to name every chip we see. So please, if you have knowledge about what is inside the Osborne 1, share it with us.
Mechanical
Mechanical
The keyboard is a throwback to the era of typewriters.
Typical connection
Typical connection
No solder used for this connection.
Pins
Pins
This connection system could not be any more familiar.
Oak Switch Systems, Inc.
Oak Switch Systems, Inc.
Oak Industries was eventually acquired by Corning Inc.
Steel plate
Steel plate
The keyboard assembly is mounted on a steal plate.
Keyboard assembly
Keyboard assembly
Not much electronics to look at in the keyboard.
Spring
Spring
The mechanical system for the keyboard reminds me of a recent TechRepublic Photo Gallery: Mod your computer keyboard, steampunk style.
The familiar latch
The familiar latch
The keyboard connects to the Osborne 1 using a ribbon cable and latch system.
Open the latch
Open the latch
Easily removed
Easily removed
The keyboard can be easily removed and then reattached.
Plastic
Plastic
Our Osborne 1 has seen some time in a basement, attic, or some other place were the plastic could lose some of its strength. Notice that some of the screw holes have deprecated to the point where they don’t actually hold the cover to the case anymore.
Nothing last forever
Nothing last forever
From this angle you can see where the some of the screw holes have disintegrated.
Getting inside
Getting inside
Apparently our Osborne 1 has been cracked open before — there are several screws missing and later on I discover screws that just don’t belong.
Mostly floppy drive
Mostly floppy drive
With the case removed the most dominate parts seem to be the floppy drives.
A cathode ray tube
A cathode ray tube
Our first look at the cathode ray tube for our display. This is by far the heaviest part in the Osborne 1.
More to come
More to come
The remaining circuit board is associated with the power system. I have no idea what those scratches on the plastic frame is all about.
Chips ahoy!
Chips ahoy!
Our Osborne 1 doesn’t skimp when it comes to the overall number of chips.
Previous incursion explained
Previous incursion explained
Apparently our Osborne 1 was upgraded with the double density floppy disk drive controller daughter board. I cannot explain why several screws went missing during that upgrade or subsequent maintenance.
The other end
The other end
The CPU can be found on this end of the board. The Osborne 1 used the Zilog Z80 processor running at 4MHz. Or at least a processor based on the Z80.
Memory banks
Memory banks
64K RAM takes up more room then you might think in 1981.
Hello Moto
Hello Moto
These memory chips were provided by Motorola.
Except for that chip in the upper left corner. Perhaps this Osborne 1 was opened more than once.
International
International
Even in 1981, PC making was an international effort. You can see stamps from the Philippines, El Salvador, and Brazil.
Call to experts
Call to experts
Okay all you engineers out there — what are the two chips from the Philippines for?
NEC
NEC
This Osborne 1 has the NEC version of the Z80 processor.
Fujitsu
Fujitsu
The large chip above the unknown one from the Philippines is from Fujitsu. According to the chip’s data sheet it is a Floppy Disk Formatter / Controller. That makes sense because of the floppy disk connection right next to the chip.
ROM
ROM
Which ROM is this?
Printer connection
Printer connection
Details
Details
Here are some more details about the origin of our Osborne 1.
You are my density
You are my density
A close up look at the double-density controller board.
Power regulation
Power regulation
There certainly are a lot of capacitors.
Danger!
Danger!
I guess it is dangerous – I was careful.
No leaks
No leaks
Over 25 years old and no leaks — take that Dell.
Fuse
Fuse
The Osborne 1 uses an old fashioned fuse. I wonder if this had to be replaced before?
More international flavor
More international flavor
The CRT, at least in part, seems to be from our friends at the Nippon Electric Company in Japan.
3M
3M
Get the parts where you get the parts.
Floppy disk drive
Floppy disk drive
The floppy drives are called full-sized but this is ridiculous. This drive is almost the size of a modern notebook computer.
Belt driven
Belt driven
The drive mechanism is belt driven — seems to be asking for failure.
Floppy chips
Floppy chips
It took quite a bit of computing power to read and write files to a floppy disk in 1981, if the number of chips involved can be used as a measure.
Look at all that space
Look at all that space
No wonder later iterations of the floppy drive were cut in half — most of this drive is wasted empty space.
Another country
Another country
More international evidence — Malaysia is represented.
Engineer help needed
Engineer help needed
Okay, I need some help here. Is that part with the “wings” a heat sink?
Floppy drive
Floppy drive
The end
The end
There were a surprisingly large number of parts in the Osborne 1. I will be interesting to see if the TRS-80 Model 4P has as many.
