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Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer

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Re: Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer

#31

Post by abritinthebay »

progman wrote: post #28

There is a lot of documentation about the Alto. Are there also complete circuit diagrams? I am just curious because the processor was made in TTL at a time before the 6502 and Z80 were born. Sooner or later the last functional Xerox Alto will cease to work (sadly). In that case it could make sense to replace the dysfunctional parts with modern retro circuits. I wonder if a project to build a functional Alto clone (wi…

As it's a TTL (with 4 74181 MSI chips) wouldn't it be possible to just grok it from the circuit board..?

Re: Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer

#32

Post by orionblastar »

progman wrote: post #28

There is a lot of documentation about the Alto. Are there also complete circuit diagrams? I am just curious because the processor was made in TTL at a time before the 6502 and Z80 were born. Sooner or later the last functional Xerox Alto will cease to work (sadly). In that case it could make sense to replace the dysfunctional parts with modern retro circuits. I wonder if a project to build a functional Alto clone (wi…

I'm sure if they can make an adapter to use SIMM or DIMM RAM chips and bypass the bad memory chips. Use a SDCard instead of hard drives to store the OS and programs on.

I guess someone could just write an emulator for the Raspberry PI and Linux or something based on the design of the Xerox Alto and how the chips function.

It seems there are emulators or simulators for Xerox Alto out there already:

http://toastytech.com/guis/salto.html

http://altogether.brouhaha.com/

To help out would be the source code to the Xerox Alto: http://www.computerhistory.org/collections/catalog/102706061

It was released and I am sure the team can make modifications to it to make it run with modern retro hardware.

Re: Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer

#33

Post by kens »

progman wrote: post #28

There is a lot of documentation about the Alto. Are there also complete circuit diagrams? I am just curious because the processor was made in TTL at a time before the 6502 and Z80 were born. Sooner or later the last functional Xerox Alto will cease to work (sadly). In that case it could make sense to replace the dysfunctional parts with modern retro circuits. I wonder if a project to build a functional Alto clone (wi…

All the Alto schematics are available at Al Kossow's Bitsavers [1]. If you want to understand how it works, start with the hardware manual [2]. The Alto processor could probably be kept running indefinitely, since it uses standard parts that can be replaced. The monitor is more difficult; the Living Computer Museum made some new monitor boards for their Altos, cloning the existing boards. The disk drives are another potential maintenance nightmare; I wonder if it would be possible to build a flash-based disk emulator.

Making a FPGA-based Alto clone would be a possibility.

[1] http://bitsavers.org/pdf/xerox/alto/schematics

[2] http://bitsavers.org/pdf/xerox/alto/AltoHWRef.part1.pdf

Re: Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer

#34

Post by Someone »

gumby wrote: post #21

I used the Alto at MIT (and for fun when I worked at PARC -- we had more powerful machines by then). There are two other things about the alto that have really stuck in my mind. First, the whole thing uses only 300 SSI and MSI TTL chips! No higher order chips (no LSI, much less VLSI). The other is that the bus bandwidth was only 3/2 the screen update rate. Updating the screen was really important: this was a user-cen…

"First, the whole thing uses only 300 SSI and MSI TTL chips! No higher order chips (no LSI, much less VLSI)."

I guess that makes it easier to reverse-engineer the hardware. I know it will be destructive, but does anybody know how many of these machines the visual6502.org team would need to do that?

Re: Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer

#35

Post by kps »

gumby wrote: post #21

I used the Alto at MIT (and for fun when I worked at PARC -- we had more powerful machines by then). There are two other things about the alto that have really stuck in my mind. First, the whole thing uses only 300 SSI and MSI TTL chips! No higher order chips (no LSI, much less VLSI). The other is that the bus bandwidth was only 3/2 the screen update rate. Updating the screen was really important: this was a user-cen…

  > most glass TTYs (think ADM-3A, Hazeltine, VT-52, and I believe
  > the 3270 as well) were taller than they were wide
That's mistaken.

http://terminals.classiccmp.org/wiki/index.php/Lear_Siegler_...

http://terminals.classiccmp.org/wiki/index.php/Hazeltine_100...

http://terminals.classiccmp.org/wiki/index.php/DEC_VT52

https://en.wikipedia.org/wiki/IBM_3270

Edit: Yes, I should have replied to the other comment…

Re: Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer

#36

Post by rjsw »

Someone wrote: post #34
gumby wrote: post #21

I used the Alto at MIT (and for fun when I worked at PARC -- we had more powerful machines by then). There are two other things about the alto that have really stuck in my mind. First, the whole thing uses only 300 SSI and MSI TTL chips! No higher order chips (no LSI, much less VLSI). The other is that the bus bandwidth was only 3/2 the screen update rate. Updating the screen was really important: this was a user-cen…

"First, the whole thing uses only 300 SSI and MSI TTL chips! No higher order chips (no LSI, much less VLSI)." I guess that makes it easier to reverse-engineer the hardware. I know it will be destructive, but does anybody know how many of these machines the visual6502.org team would need to do that?

Why reverse engineer anything ?

Just look up the logic diagram in your copy of The TTL Data Book.

Re: Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer

#37

Post by Animats »

Animats wrote: post #22

I haven't used one of those in a long time. Stanford had several Alto machines, but they didn't have Smalltalk, due to some licensing issue. They just ran standalone Mesa programs. When I was at Stanford, few people wanted to use the obsolete Altos, so time on them was available. So I did a small project on them. Bravo was used as both the text editor and the word processor. The file format was plain text, then a con…

I just looked in some boxes I haven't opened in decades. I have "Mesa Language Manual, Version 5.0, April 1979". If the people with the Alto need this, let me know.

If the world had used Mesa instead of C, computing would have been far less buggy. Mesa was a hard-compiled language, but it had concurrency, monitors, co-routines ("ports", similar to Go channels), strong type safety, and a sane way to pass arrays around. In the 1970s.

(I should donate this stuff to the Computer Museum. I just found the original DEC Small Computer Manual, many 1960s UNIVAC mainframe manuals, and a reel of UNIVAC I steel magnetic tape.)

Re: Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer

#38

Post by eschaton »

Animats wrote: post #37
Animats wrote: post #22

I haven't used one of those in a long time. Stanford had several Alto machines, but they didn't have Smalltalk, due to some licensing issue. They just ran standalone Mesa programs. When I was at Stanford, few people wanted to use the obsolete Altos, so time on them was available. So I did a small project on them. Bravo was used as both the text editor and the word processor. The file format was plain text, then a con…

I just looked in some boxes I haven't opened in decades. I have "Mesa Language Manual, Version 5.0, April 1979". If the people with the Alto need this, let me know. If the world had used Mesa instead of C, computing would have been far less buggy. Mesa was a hard-compiled language, but it had concurrency, monitors, co-routines ("ports", similar to Go channels), strong type safety, and a sane way to pass arrays around…

Please, both of you, get in touch with Al Kossow at the Computer History Museum about preserving these important pieces of our heritage.

Re: Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer

#39

Post by cpr »

gumby wrote: post #30
kens wrote: post #24

Earlier quoted context omitted.

Thanks for the info, gumby. As you point out, the amount of bus bandwidth consumed by the display is a big thing. It seems a bit crazy that the processor was running microcode to copy all the pixels to the display in 16-word chunks, 30 times a second. (In a "normal" system, the video hardware fetches characters or pixels from memory. But in the Alto, the processor was running instructions to feed the pixels to the di…

> It seems a bit crazy that the processor was running microcode to copy all the pixels to the display It seems crazy today but not in context. There wasn't video hardware in today's sense. There were either mainframes (with channel controllers) with the terminal doing the "rendering" or minicomputers and microcomputers in which the CPU did everything (which is what I guess it was like before the mainframe era). You c…

Ah yes, Ambassadors! Portrait mode "dumb" terminals, but highly valued for coding given their 48 lines of text. (Twice the normal in the VT-100 days.)

Had a lot of those first at the Columbia computer center back in the DEC-20 days, later at the Fairchild AI Lab startup (DEC-20's and LISPMs), and even later at Imagen (a Stanford TeX project spinoff building the first commercial laser printers before Apple and Xerox released theirs).

Re: Y Combinator's Xerox Alto: restoring the legendary 1970s GUI computer

#40

Post by Someone »

rjsw wrote: post #36
Someone wrote: post #34

Earlier quoted context omitted.

"First, the whole thing uses only 300 SSI and MSI TTL chips! No higher order chips (no LSI, much less VLSI)." I guess that makes it easier to reverse-engineer the hardware. I know it will be destructive, but does anybody know how many of these machines the visual6502.org team would need to do that?

Why reverse engineer anything ? Just look up the logic diagram in your copy of The TTL Data Book.

Are all of them standard ones? If so, you're 100% right.

Also, I just saw https://news.ycombinator.com/item?id=11930327, which states: "All the Alto schematics are available at Al Kossow's Bitsavers [1]. If you want to understand how it works, start with the hardware manual [2]"

That must make this one of the easiest pieces of hardware to keep running, at least for the digital parts (monitor and hard disk are more of a problem, I understand)

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