7 ms·

According to Paul Allen's book [1] about his time at Microsoft (admittedly a biased source), his particularly critical contribution was an 8088 emulator/simulat

According to Paul Allen's book [1] about his time at Microsoft (admittedly a biased source), his particularly critical contribution was an 8088 emulator/simulator for the PDP-10. That allowed them to write and even interactively debug (if I remember right) BASIC for the 8088 on the PDP. It would've been hopeless to develop directly on a microcomputer, so they would've had to have written on the minicomputer, transferred the binary across and see if it worked, and iterate like that. That contribution wouldn't show up directly in the BASIC source code, since the emulator wasn't part of BASIC itself. [1] https://www.amazon.co.uk/Idea-Man-Memoir-Co-founder-Microsoft/dp/0241953715 https://www.amazon.co.uk/Idea-Man-Memoir-Co-founder-Microsof...

PaulHoule 5y ago
Using a minicomputer as a dev environment for micros was particularly popular in the late 1970s and early 1980s. See Infocom https://www.filfre.net/2013/03/the-top-of-its-game/ https://www.filfre.net/2013/03/the-top-of-its-game/ which used virtual machine technology to deliver games developed on a Decsystem 20 to many different kinds of Micro. When Microsoft BASIC came out in 1976 it was rare for a micro to fill out the 16-bit address space with a full 64k. I had a TRS-80 Color Computer which ran a multitasking operating system https://en.wikipedia.org/wiki/OS-9 https://en.wikipedia.org/wiki/OS-9 With 64k of RAM I wrote a FORTH interpreter that ran under OS-9 with a good standard library in about 3000 lines of assembly. OS-9 looked a lot like UNIX or VMS. Dev tools in 1984 were good enough that writing a BASIC interpreter on a micro in assembly would have been straightforward, I'm sure you could on a C-64. No way you could do that on the base configuration Altair that Microsoft BASIC originally targeted. The first time I used emulation was circa 1987 when I developed a BASIC program for a high school teacher who had a Z-80 based CP/M system on my generic 286 machine... Even then there was a CP/M emulator for the 286 which could destroy any Z-80 machine on the market -- even though the protected mode of the 286 was as "brain damaged" as Bill Gates said it was, the raw performance of the 286 was the beginning of the end for the 6502, 68--, 68---, Z80 and all the other architectures.
- dunham 5y ago
  I had an obscure machine ("Interact") in the early 80's that had an 8080, 16 kb of memory, and a cassette drive. There was an assembler for it. If I remember right, you read the editor from tape, edit and save your file, then read the assembler from tape, it reads the tape with your code and then writes the output to tape. I have no idea what the people ("Micro Video") producing software for this thing did, but I can't imagine they used this on-machine assembler. (The tape loading mechanism was basically blocks of address + data. They put loading screens on the tapes by populating video memory first.)
hougaard 5y ago
... an 8080 emulator, not 8088 :)
scionthefly 5y ago
So I might be able to use a PiDP-11 microcomputer, presuming it is compatible with thd PDP-10, to run an 8088 emulator, on which I could run early DOS programs?
- aidenn0 5y ago
  PDP-11 and PDP-10 are completely different. The 11 was in the DEC 16-bit series and the 10 was in the DEC 36-bit series.
  - cbm-vic-20 5y ago
    While this is completely true, the PiDP-11 mentioned by the parent is based on SimH, which does simulate PDP-10 (as well as dozens of other early systems). [1] https://obsolescence.wixsite.com/obsolescence/pidp-11 https://obsolescence.wixsite.com/obsolescence/pidp-11 [2] https://github.com/simh/simh https://github.com/simh/simh
unfocussed_mike 5y ago
Yes. There's an even more extraordinary story about them travelling to demonstrate their implementation of BASIC to the MITS team. They realise they have not written a bootloader for the Altair, and Allen writes out a bootloader on the plane, which works when they get to MITS. https://en.wikipedia.org/wiki/Altair_BASIC#Origin_and_development https://en.wikipedia.org/wiki/Altair_BASIC#Origin_and_develo... My first encounter with a real Microsoft BASIC wasn't for another 15 years; the interpreter-only QBASIC that came with Halvorson & Rygmyr's Learn BASIC Now, which was a great book I gave away and now feel the urge to repurchase for nostalgia's sake. I used it for my GCSE Computer Science project.
- WalterBright 5y ago
  Writing an 8080 emulator on the -10 is not extraordinary, after all, it's a trivial instruction set. What was extraordinary is Allen realizing he could do this as a shortcut.
  - WalterBright 5y ago
    An 8080 has what, 40 opcodes? All doing simple things like "add" and "mov". https://altairclone.com/downloads/manuals/8080%20Programmers%20Manual.pdf https://altairclone.com/downloads/manuals/8080%20Programmers...
    - phkahler 5y ago
      I learned on an 8080 system (Interact) that also had MS basic. Almost every one of 256 op-codes is used on the 8080. That's not to say there were that many instructions. For example register-to-register move might be considered one instruction but the source and destination register are encoded into that one byte so there are many reg-reg moves. Same with add sub, etc... My father wrote a disassembler in basic to read out the ROM and he made his own mnemonics which amounted to probably 20-40 actual instructions (I still have it and could look it up), but there were maybe 8 entries in the opcode table that did nothing.
      - 5y ago
deleted 5y ago
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PaulHoule 5y ago

Using a minicomputer as a dev environment for micros was particularly popular in the late 1970s and early 1980s. See Infocom https://www.filfre.net/2013/03/the-top-of-its-game/ https://www.filfre.net/2013/03/the-top-of-its-game/ which used virtual machine technology to deliver games developed on a Decsystem 20 to many different kinds of Micro. When Microsoft BASIC came out in 1976 it was rare for a micro to fill out the 16-bit address space with a full 64k. I had a TRS-80 Color Computer which ran a multitasking operating system https://en.wikipedia.org/wiki/OS-9 https://en.wikipedia.org/wiki/OS-9 With 64k of RAM I wrote a FORTH interpreter that ran under OS-9 with a good standard library in about 3000 lines of assembly. OS-9 looked a lot like UNIX or VMS. Dev tools in 1984 were good enough that writing a BASIC interpreter on a micro in assembly would have been straightforward, I'm sure you could on a C-64. No way you could do that on the base configuration Altair that Microsoft BASIC originally targeted. The first time I used emulation was circa 1987 when I developed a BASIC program for a high school teacher who had a Z-80 based CP/M system on my generic 286 machine... Even then there was a CP/M emulator for the 286 which could destroy any Z-80 machine on the market -- even though the protected mode of the 286 was as "brain damaged" as Bill Gates said it was, the raw performance of the 286 was the beginning of the end for the 6502, 68--, 68---, Z80 and all the other architectures.

dunham 5y ago
I had an obscure machine ("Interact") in the early 80's that had an 8080, 16 kb of memory, and a cassette drive. There was an assembler for it. If I remember right, you read the editor from tape, edit and save your file, then read the assembler from tape, it reads the tape with your code and then writes the output to tape. I have no idea what the people ("Micro Video") producing software for this thing did, but I can't imagine they used this on-machine assembler. (The tape loading mechanism was basically blocks of address + data. They put loading screens on the tapes by populating video memory first.)

hougaard 5y ago

... an 8080 emulator, not 8088 :)

scionthefly 5y ago

So I might be able to use a PiDP-11 microcomputer, presuming it is compatible with thd PDP-10, to run an 8088 emulator, on which I could run early DOS programs?

aidenn0 5y ago
PDP-11 and PDP-10 are completely different. The 11 was in the DEC 16-bit series and the 10 was in the DEC 36-bit series.
- cbm-vic-20 5y ago
  While this is completely true, the PiDP-11 mentioned by the parent is based on SimH, which does simulate PDP-10 (as well as dozens of other early systems). [1] https://obsolescence.wixsite.com/obsolescence/pidp-11 https://obsolescence.wixsite.com/obsolescence/pidp-11 [2] https://github.com/simh/simh https://github.com/simh/simh

unfocussed_mike 5y ago

Yes. There's an even more extraordinary story about them travelling to demonstrate their implementation of BASIC to the MITS team. They realise they have not written a bootloader for the Altair, and Allen writes out a bootloader on the plane, which works when they get to MITS. https://en.wikipedia.org/wiki/Altair_BASIC#Origin_and_development https://en.wikipedia.org/wiki/Altair_BASIC#Origin_and_develo... My first encounter with a real Microsoft BASIC wasn't for another 15 years; the interpreter-only QBASIC that came with Halvorson & Rygmyr's Learn BASIC Now, which was a great book I gave away and now feel the urge to repurchase for nostalgia's sake. I used it for my GCSE Computer Science project.

WalterBright 5y ago
Writing an 8080 emulator on the -10 is not extraordinary, after all, it's a trivial instruction set. What was extraordinary is Allen realizing he could do this as a shortcut.
- WalterBright 5y ago
  An 8080 has what, 40 opcodes? All doing simple things like "add" and "mov". https://altairclone.com/downloads/manuals/8080%20Programmers%20Manual.pdf https://altairclone.com/downloads/manuals/8080%20Programmers...
  - phkahler 5y ago
    I learned on an 8080 system (Interact) that also had MS basic. Almost every one of 256 op-codes is used on the 8080. That's not to say there were that many instructions. For example register-to-register move might be considered one instruction but the source and destination register are encoded into that one byte so there are many reg-reg moves. Same with add sub, etc... My father wrote a disassembler in basic to read out the ROM and he made his own mnemonics which amounted to probably 20-40 actual instructions (I still have it and could look it up), but there were maybe 8 entries in the opcode table that did nothing.
    - 5y ago

deleted 5y ago

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