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The technical documentation was really good. Complete BIOS listing (that as fun to read), and IIRC there were circuit diagrams (since there was very little VLSI
by kabdib 5y ago
The technical documentation was really good. Complete BIOS listing (that as fun to read), and IIRC there were circuit diagrams (since there was very little VLSI -- just the processor, memory, and a bunch of gate-level TTL chips).
I think that BIOS listing sealed IBM's fate to lose control of the platform; it made it near trivial for a competitor to analyze and shove under the doorway of a "clean room" team to reimplement.
- chadcmulligan 5y agoA lot of things had circuit diagrams then, I did chip level repairs on Kaypro clones, and CP/M machines at the time, and it was all TTL off the shelf chips. You could follow the signals through the diagram with a logic probe, clip out the broken gates, clean the board, and pop in a new one, it was very satisfying.
- flohofwoe 5y agoOn the other hand, all that information was available for the Amiga too (and probably also Atari), in fact it was quite normal on home computers to get the complete hardware schematics in the box, and the ROM were quickly disassembled and commented by hobbyists. The IBM PC was probably an outlier for the "business world" though.
- actually_a_dog 5y agoThat's interesting. My first computer was a TI-99/4a, and I don't remember seeing stuff like BIOS listings in the documentation. I don't have any of that stuff anymore, so, I could be wrong.
- flohofwoe 5y agoThe ROM listings were usually "third party" efforts, for instance in Germany there was a fairly popular (among home computer enthusiasts) "xxx Intern" book series where most of the book consisted of the annotated ROM disassembly. For instance "CPC Intern": http://www.cpcwiki.eu/index.php/CPC464_Intern http://www.cpcwiki.eu/index.php/CPC464_Intern
- incanus77 5y agoNo, you're right. The TI-99 was notoriously closed and anti-hobbyist. It was my first as well, and I recently got my hands on one again (though a later, reduced-cost beige-case one). It's remarkable how opaque the system is. Contrast this with my Commodore 128 or TRS-80 Model 100, which ship with schematics, opcode info, etc. and had a healthy book ecosystem around them. I hit my limits with the relatively weak TI-BASIC, but having nowhere else to go (even with the technical "green manual"), I wonder what I would have gotten up to had there been more there like a built-in assembler. Then again, the thing did ship in 1979 initially and was the first home 16-bit machine (technically).
- ddingus 5y agoAtari was closed in these ways. No schematic, no ROM listing. Others filled in gaps, but it was noticed then. I noticed. Apple and PC computers cost more. At one point then, being open seemed worth more to me.
- kabdib 5y agoAtari published the listings of the ROMs for their 400/800 line of computers. They also published the BIOS for the Atari ST (which I helped write, and wrote the documentation for). No schematics, though.
- ddingus 5y agoYes, that is as I recall too. Really, I was speaking to what came with the machines. Buy an Apple, and get schematics, ROM listing, etc, and there it all is in the open. And it was ready to use. An Atari was a different experience. Was not ready to program, and technical details took a while to be published. My first "PC" was an Apple 2. My first machine was an Atari. My first IBM type PC was much closer to the Apple than it was Atari.
- MichaelZuo 5y agoMakes sense why technical specifications are closely guarded nowadays.
- nradov 5y agoIn order to avoid copyright violation, Compaq did clean room reverse engineering of the IBM PC BIOS in order to build the first clone. They didn't use any code listing.