EEVblog #1053 - The Biggest 80's Computer FAIL - IBM PC Jr

[EEVblog]

Dave looks at the biggest flop in 1980's personal computers, the IBM PC Jr.
Teardown and extensive walk-through of the main motherboard.

Service Manual: http://www.retroarchive.org/dos/docs/ibmpcjrtechref.pdf




Part 2: Troubleshooting -

[blacksheeplogic]

Not really convinced a business exec would have bought one of these for connectivity with the central systems (uncommon business requirement). Lugables fulfilled that role.

[Bud]

The rubber belt on the motor in the floppy drive was still good 

[floobydust]

Nobody I knew could afford real IBM hardware. Price was the big killer of the Jr.

I remember the XT clones from Taiwan were coming in around 1985, much lower price so that's what I bought. DRAM and two floppy drives were very expensive back then, and you needed a decent monitor on top of that. NTSC couldn't do 80 column text unless you like fuzzy fonts.

[McBryce]

The trimmer pot for the disk spin speed is in the motor. There's a hole with a grey rubber plug on top of the motor and the pots behind that.
The controller is a 765, so it could only handle up to Double Density disks at best.

McBryce.

[amspire]

The first PC I bought in the mid 80's was shared with my brother - a 20MHz 286 clone motherboard. We got the extended memory card with 4M, but at the time there was a huge RAM shortage, so I think the PC cost A$6000 with the memory card worth $4000 of that. Probably could almost buy a car for that money.

Never even considered buying an IBM PC. I do remember walking into Computerland at the time and quickly walking out again when the IBM prices were mentioned.

I do remember seeing an ad from a few years earlier. This was a meant to be a special price. A fully configured IBM XT for A$12,000. The gigantic 20MByte hard drive, of course. None of that cheaper 10MByte hard drive rubbish.

[rsjsouza]

Cool videos.

"Television, believe it or not?!?" I am not sure how it was in Australia, but in the 80's in Brazil only the really wealthy would buy an actual computer monitor with composite inputs to be used on a home computer - TVs with composite inputs were unheard of, and we always had to rely on the infamous ch3/4 and the antenna/console switch box.  Only later came the green phosphorous monitors with the more modern PC-XTs...

FCC emissions regulations were really strict at the time, thus people really over engineered the shielding on the cables, cases, etc. Several developers of the time mention that (I recall Bil Herd's account on the Commodore Book).

IIRC 5-¹/₄ single sided were either 120kB or 180kB (if Double Density). Double-sided floppies were 360kB.

For the longest time AMD manufactured processors for Intel under license. IIRC they started to drift apart in the mid 1990s.

According to the schematics (appendix B of this Tech Ref with schematics) the unkonwn Motorola part is yet another ROM (MK34000 - 2048x8) - perhaps the BASIC? It looks too small to be either DOS or BIOS.

The IBM part 1503730 is a gate array to generate composite video - totally custom. In some cheaper computers of the time (Sinclair, for example), National had the LM1889 to do that.

[james_s]

IBM made a bet with the PC Jr and they bet wrong. I suspect it was a situation of design by committee where some management person decided that things like the proprietary ports were a brilliant idea and that the keyboard was good enough. I can almost hear the engineers arguing that it made sense to use the same ISA bus as the full fledged PC only to be shot down by management insisting that they don't want to cannibalize their higher margin business PC market. It may well have succeeded if not for the fact that PC clones far superior to the PC Jr flooded the market at competitive prices.

Curiously IBM did not learn their lesson when they went on to design and market the PS/2 line which at least was innovative and offered some real advantages. Pushing a proprietary standard, even when it was arguably superior into a market flooded by "good enough" and much cheaper more widely available ISA was doomed to failure from the start.

[Towger]

The PS/1 was another 'budget' non standard flop.  They gave them away to schools across Ireland, in conjunction with supermarket. In a scheme for parents to get points for their children's school by shopping there.  The story was that IBM had a warehouse full of PS/1s they could not get rid of.

[T3sl4co1l]

Anywhere you see proprietary connectors for an existing standard, you can bet your sweet ass it was a vendor lock-in mandate from the higher-ups.

The non-ISA edge connectors for internal devices, may've arguably been a cost saving measure, and the engineers got to play "what pins do we /really/ need for X?".  But you can bet that was yet another case.

Tim

[james_s]

IMHO the stupidest thing about the PS/1 was putting the power supply in the monitor, at that point they should all have used the all-in-one design.

At least they were software compatible with the industry standard PC/XT/AT machines as I recall. That's something the PC Jr couldn't claim.

[GeorgeOfTheJungle]

Anywhere you see proprietary connectors for an existing standard, you can bet your sweet ass it was a vendor lock-in mandate from the higher-ups.

The non-ISA edge connectors for internal devices, may've arguably been a cost saving measure, and the engineers got to play "what pins do we /really/ need for X?".  But you can bet that was yet another case.

Apple did that too in the Performa line where no two expansion cards were equal/had the same connector. Well, wth, they still do it today.

[helius]

If you're counting purely in terms of units sold, the PC Jr was much less of a flop compared to other 1980s machines like the Osborne Vixen or the Hyperion.
The PC Jr may have been the product with the most unsold stock written off, but the Apple III and Lisa were up there as well.

[james_s]

The Apple III is a turd, I have one and very quickly got bored messing with it. Steve Jobs and his OCD meddling helped to deliver some really polished products but that isn't one of them. The later IIgs is what the III should have been.

The Lisa was ahead of its time and as delivered was too little, too late, at too high a price. The Macintosh corrected many of the mistakes of the Lisa but went too far the other way away from expandability. It was not really a useful machine until the 512k version came out and then the Plus with the ability to hold a massive (for the time) 4MB of RAM and SCSI interface was revolutionary. Even so, without the 3rd party accelerators, video adapters, scanners, networking and other peripherals it may never have succeeded.

[Rotareneg]

I just stumbled upon a video showing how sensitive the IR receiver on the PCjr is to optical interference from lighting, perhaps that's why you couldn't get it to work:

[McBryce]

One of my first student jobs was in the IT department of a small Supermarket chain. I got a call from a woman at a far off branch claiming her keyboard had stopped working. Not sure what to do (it would have been a long drive over to check it out), I asked my older colleague for advice:
"Ah, that's Margaret" he says, grabs the phone from me and says "No problem Margaret, grab yourself a coffee and I'll re-activate it remotely". I was amazed that we could remotely diagnose and repair hardware. He then sat back and enjoyed his own coffee...
I asked what we needed to do he said "We do nothing, she's put her empty coffee cup in front of the IR sensor again", "When she comes back she'll put her coffee cup back beside the keyboard and think we worked wonders". Supposedly these calls came from her at least once a month.

McBryce.

[Brumby]

One of my first student jobs was in the IT department of a small Supermarket chain. I got a call from a woman at a far off branch claiming her keyboard had stopped working. Not sure what to do (it would have been a long drive over to check it out), I asked my older colleague for advice:
"Ah, that's Margaret" he says, grabs the phone from me and says "No problem Margaret, grab yourself a coffee and I'll re-activate it remotely". I was amazed that we could remotely diagnose and repair hardware. He then sat back and enjoyed his own coffee...
I asked what we needed to do he said "We do nothing, she's put her empty coffee cup in front of the IR sensor again", "When she comes back she'll put her coffee cup back beside the keyboard and think we worked wonders". Supposedly these calls came from her at least once a month.

McBryce.

Pure GOLD.   

[rsjsouza]

Good story!

[Calambres]

It reminds me of "The IT Crowd" TV series 

I worked for IBM for 30+ years, many of them in a PC support team, and NEVER saw a PC Jr.

[GeorgeOfTheJungle]

The Sinclair QL sold even worse than this, only 150k units: https://en.wikipedia.org/wiki/Sinclair_QL

[james_s]

One needs to consider the quantities of other products from the same company and the money spent developing the product in question. For a small company selling 100 units of some esoteric product that cost a few thousand to develop might be a smashing success, while for a company like IBM intending to sell millions, 100 units of something that cost millions to develop would be a colossal failure.

[GeorgeOfTheJungle]

Only 150k QLs, 500k PCJrs, 5 million Sinclair Spectrum: https://en.wikipedia.org/wiki/ZX_Spectrum

[SNGLinks]

I loved my QL. Had great fun going to the User Group meetings. There you could get help from people like Tony Tebby who wrote the QDOS operating system.

[Fungus]

The Sinclair QL sold even worse than this, only 150k units: https://en.wikipedia.org/wiki/Sinclair_QL

I could name quite a few 1980s computers which only sold a few thousand units (I used to have an extensive collection of them because the company where I worked got one of everything).

This isn't some tiny startup company though, it's IBM.

(yes, I know the QL isn't from a small startup company, it failed because of production delays, the crappy microdrives, all sorts of other reasons).

[Jacko]

The Tandy 1000 was a clone of the PC Jr. (as mentioned) though improved in a number of ways, and it came with a floppy drive!

I bought one back in the early/mid 1980s and still have it, though now it sports a 20Mb hard-card and a 3.5" floppy as well as the original 5.25". I fired it up a couple of years ago and it worked just fine...  MS-DOS 6.22 on it currently (I believe).

Update: The T1000 has Tandy DOS 3.2 on it... the 6.22 was in my old Packard Bell 286.  I don't believe the T1000 had a math coprocessor. Can't remember if it had a socket for one though I recall that I made a number of mods to it over the years.

regards, Jacko

[james_s]

My aunt had a Tandy 1000, I remember playing games on it when I was a kid. Seems like it was somewhat PC compatible but not entirely. I hadn't realized it was a clone of the PC Jr but that would make sense.