IBM 5150 POST – 'Manufacturing Test' mode | Hacker News Reader

IBM 5150 POST – 'Manufacturing Test' mode

minuszerodegrees.net

40 pointszdw13 comments

The great thing about the original IBM PC (and the XT) was the wealth of documentation you got with it (I never had an AT). I don't remember seeing the docs described in the OP, but it really was good. I had an XT, with a mono monitor on my desk, and I learned so much about the 8086, MSDOS and other things on that box.

But all IBM documentation (for mainframes, peripherals and such) was really brilliant. And their hardware was great, from big boxes to little ones. I've never really understood how they got such a bad reputation.

> I've never really understood how they got such a bad reputation.

Mostly for their business practices.

It seems like every ~generation in tech there's at least one big company doing shady abuses of their monopoly and pushing against anti-trust as hard as they can.

IBM did it for a while, 60s and 70s maybe, Microsoft was next, Google and Apple after that?

Usually the tech isn't the issue, it's how the companies throw their weight around.

Understood, and I mostly agree. My favourite story about IBM malpractices was how they upgraded one of their printers. The technician doing the upgrade ushered all client staff out of the machine room. He then moved a rubber band from one pulley onto another.

But on the other hand, they did produce some really good kit and software, which if you are a programmer is really what you want. And people like DEC were hardly adverse to doing similar stuff.

> He then moved a rubber band from one pulley onto another.

Hah, that's a good one.

> But on the other hand, they did produce some really good kit and software [...]

Yeah, agreed (though really they did all of their best work well before my time, so I only know ~some of the history).

Always thought it was funny that IBM used this product ID number:

https://www.dictionary.com/e/slang/5150/

Wow, that's hilarious.

Probably a n00b question but where did the commented machine code come from? Did IBM publish their original PC BIOS code, comments and all? Was the original "PC clone" bios just a clean room reimplementation?

Yes, there was a gray fabric covered binder that had the full source code. I got a copy somehow in the mid 80s as a teenager. I poured over the bios code which made me ace my assembler class years later in college (along with reading the pink shirt book).

oh pink shirt book...

Yes, and yes:

https://www.allaboutcircuits.com/news/how-compaqs-clone-comp...

It was published, comments and all. Copyright.

And the award for most innovative use of the manufacturing test mode goes to reenigne (of 8088MPH fame), who used it to make a web service that runs user-submitted snippets of 8086 code on a genuine IBM XT:

http://www.reenigne.org/xtserver/

That's some oddly specific trivia, but the index page for that site looks like a great resource of technical information on the original PC line of computers.

http://minuszerodegrees.net/index.htm

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