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Hardware

Cracking open the Osborne 1: The original portable computer

By Mark W. Kaelin March 19, 2008, 12:52 AM PDT

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Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

Mechanical

Mechanical

The keyboard is a throwback to the era of typewriters.

Cracking open the Osborne 1: The original portable computer

Typical connection

Typical connection

No solder used for this connection.

Cracking open the Osborne 1: The original portable computer

Pins

Pins

This connection system could not be any more familiar.

Cracking open the Osborne 1: The original portable computer

Oak Switch Systems, Inc.

Oak Switch Systems, Inc.

Oak Industries was eventually acquired by Corning Inc.

Cracking open the Osborne 1: The original portable computer

Steel plate

Steel plate

The keyboard assembly is mounted on a steal plate.

Cracking open the Osborne 1: The original portable computer

Keyboard assembly

Keyboard assembly

Not much electronics to look at in the keyboard.

Cracking open the Osborne 1: The original portable computer

Spring

Spring

The mechanical system for the keyboard reminds me of a recent TechRepublic Photo Gallery: Mod your computer keyboard, steampunk style.

Cracking open the Osborne 1: The original portable computer

The familiar latch

The familiar latch

The keyboard connects to the Osborne 1 using a ribbon cable and latch system.

Cracking open the Osborne 1: The original portable computer

Open the latch

Open the latch

Cracking open the Osborne 1: The original portable computer

Easily removed

Easily removed

The keyboard can be easily removed and then reattached.

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

Nothing last forever

Nothing last forever

From this angle you can see where the some of the screw holes have disintegrated.

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

Mostly floppy drive

Mostly floppy drive

With the case removed the most dominate parts seem to be the floppy drives.

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

Chips ahoy!

Chips ahoy!

Our Osborne 1 doesn’t skimp when it comes to the overall number of chips.

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

Memory banks

Memory banks

64K RAM takes up more room then you might think in 1981.

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

International

International

Even in 1981, PC making was an international effort. You can see stamps from the Philippines, El Salvador, and Brazil.

Cracking open the Osborne 1: The original portable computer

Call to experts

Call to experts

Okay all you engineers out there — what are the two chips from the Philippines for?

Cracking open the Osborne 1: The original portable computer

NEC

NEC

This Osborne 1 has the NEC version of the Z80 processor.

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

ROM

ROM

Which ROM is this?

Cracking open the Osborne 1: The original portable computer

Printer connection

Printer connection

Cracking open the Osborne 1: The original portable computer

Details

Details

Here are some more details about the origin of our Osborne 1.

Cracking open the Osborne 1: The original portable computer

You are my density

You are my density

A close up look at the double-density controller board.

Cracking open the Osborne 1: The original portable computer

Power regulation

Power regulation

There certainly are a lot of capacitors.

Cracking open the Osborne 1: The original portable computer

Danger!

Danger!

I guess it is dangerous – I was careful.

Cracking open the Osborne 1: The original portable computer

No leaks

No leaks

Over 25 years old and no leaks — take that Dell.

Cracking open the Osborne 1: The original portable computer

Fuse

Fuse

The Osborne 1 uses an old fashioned fuse. I wonder if this had to be replaced before?

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

3M

3M

Get the parts where you get the parts.

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

Belt driven

Belt driven

The drive mechanism is belt driven — seems to be asking for failure.

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

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.

Cracking open the Osborne 1: The original portable computer

Another country

Another country

More international evidence — Malaysia is represented.

Cracking open the Osborne 1: The original portable computer

Engineer help needed

Engineer help needed

Okay, I need some help here. Is that part with the “wings” a heat sink?

Cracking open the Osborne 1: The original portable computer

Floppy drive

Floppy drive

Cracking open the Osborne 1: The original portable computer

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.

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By Mark W. Kaelin
Mark W. Kaelin has been writing and editing stories about the information technology industry, software, hardware, gaming, finance, accounting, and technology geekdom for more than 30 years.
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