40 Years Of The PC - We Recover An Original IBM PC
Written by Harry Fairhead   
Monday, 16 August 2021
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40 Years Of The PC - We Recover An Original IBM PC
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The motherboard as work of art?

I spotted it hanging on the wall. It definitely was what I thought it was – an original PC motherboard complete with all chips including RAM. Why it was hanging on a wall was a mystery, but presumably someone thought it was a work of art! I vaguely remembered that the original PC that it came out of was hidden in a loft somewhere and in honour of its birthday an expedition seemed in order – so I got a someone much younger to get a ladder and go and find it!

It didn’t need much searching and no special instruments to find the resting place of the old machine. When the team picked it up the first comment was – “what’s in this thing?” I’d forgotten how much metal was in an original PC case – in a 30mph collision with a modern machine the passengers in the IBM PC would surely survive with just scratches. The second surprise was finding the original monitor – a chunky thing with a surprisingly small screen. After we got the whole thing down, I realised one of the team was missing. Yelling up into the loft I discovered that he was still searching for the mouse – I left him to it…

No Mouse

The early PC didn’t have much that the modern user has come to expect and a mouse certainly wasn’t one of them. I joked that it did have a colour monitor, however, as long as you considered green on black to be sufficient.

Then we managed to slide the cover off and reveal what was inside – an old 286 motherboard had replaced the original. Clearly upgrading isn’t a new invention and was practiced by the primitive people who owned, and probably worshipped, this artefact. After some careful brushing away of the dust, and much sneezing, it was clear that things had indeed changed much. The huge black objects to the front were eventually identified as a floppy disk and a hard disk. One of the assistants commented that the hard drives capacity must have been very big to need such a large volume. On uncovering the drives label there was much argument over what “10M” was supposed to mean –surely it couldn’t be 10Megabytes. The next surprise was the way that the hard disk wasn’t IDE but had two ribbon cables running to a large hard disk controller card. The amazing thing was that the floppy disk had a completely separate controller and it too was huge!

The first task in restoration was to remove the motherboard of a later vintage and put the original board back in place. A box full of old, and very large cards also provided an original MDA – that’s Monochrome Display Adapter to you! As the motherboard had all of its memory intact, an entire 512KBytes, there was no problem in trying the whole thing out. The bright green solid display was soon looking as good as ever but seeing it all working also prompted a few additional questions from the "younger" members of the team (remember anyone under 40 wasn’t born when the IBM PC came out) that don’t usually get asked:

Why does the screen look so, so … solid?

The answer is that the original monitor had a long persistence phosphor that glowed long after you switched it off – in this case you really did need a screen saver for perhaps the first and last time in the history of the PC.

Did you really manage with only 10MBytes of disk storage?

The answer is not only that but most PCs didn’t have a hard disk and the users managed with 360KBytes of floppy disk storage. You have to keep in mind that data was mostly text based – we didn’t really use graphics much and we certainly didn’t save such things to disk.

What did you do about booting the machine when it had no hard disk?

MS-DOS fitted on a 360KByte floppy and you simply stuck a DOS disk in the drive to get the machine started. PC-DOS 1.0 didn’t even support a hard disk.

OK where does the mouse plug in?

Er sorry no mouse. That wasn’t needed until we had graphics and that’s much further down the road.

Which one of the big expansion cards is the sound card?

Very funny! Sound was one of the very last of the multimedia facilities to be standardised. Creative labs launched the SoundBlaster card in 1988 but it still took time to catch on. All the PC had was a speaker that could go beep – but it could be made to do clever things with the right software.

Why was the keyboard so big and heavy?

Because of the success of the IBM Selectric Typewriter which most typists claim is the best keyboard ever made. The PC also had to have a good keyboard to be taken seriously.

OK, so given you didn’t have graphics, a mouse or sound what did you do with the thing?

There were personal computers before the IBM PC hit the streets so it wasn’t like it was something completely new. The machine shipped with PC-DOS(i.e. MS-DOS) and CPM/86. We had BASIC, Fortran and Cobol to program in and spreadsheet to play with. Computer games? Not really, not as you’d understand them today.

How fast was it?

The clock speed was only 4.77MHz which seemed fast at the time. The processor was only a halfway between 8 and 16 bits as well so it wasn’t as powerful as you might think. It also didn’t have any memory management hardware – 1MByte really was its top limit until people added additional hardware to extend it. But it was fast enough because, see earlier answer, we only used it for text and limited numeric data.

No CD-ROM! How did you get software onto it?

Floppy disk - 5.25" floppy disk to be exact and they really were bendable. As the software used didn’t have much in the way of a user interface it mostly fitted on a few floppy disks. It even ran from floppy disks in most cases.

I suppose there’s no point in asking about modems and the Internet?

You’re catching on! Actually there were modems but there really wasn’t anyone to call. In place of the Internet we, eventually, had Bulletin Boards and a strange online version of teletext called Prestel.

floppydisk

8", 5.25" and 3.5" floppy disks. 



Last Updated ( Monday, 16 August 2021 )