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

http://www.righto.com/2016/06/y-combinators-xerox-alto-restoring.html

by kens • 10 years ago

300 105 10 years ago

dom96• 10 years ago

My first impressions of it are that the portrait oriented monitor actually looks very stylish. There is something almost futuristic about it.

krylon2• 10 years ago

These days, some displays allow you to rotate them between landscape and portrait orientiation.

At work, I have a 24 inch TFT in portait mode which I use mostly for coding (and other tasks where vertical space is valuable). It is very nice, because e.g. in text processing, a whole page fits the screen nicely.

In a way, we have that with tablets and phones, too.

brudgers• 10 years ago

Operating systems and drivers will allow rotation of most monitors and it mainly comes down to a matter of mounting hardware if autorotation isn't a big deal. Monoprice has a stand for about $20.

http://www.monoprice.com/product?c_id=108&cp_id=10828&cs_id=...

semi-extrinsic• 10 years ago

For years I've used an old 19" LCD in portrait mode next to a new-ish 24". The display heights (after rotating the 19") are identical, and the vertical resolutions are almost identical (1080 vs 1024). It's a cheap/free way of getting a wider screen. Usually I keep some paper or reference document on the 19" and have two side-by-side terminals on the 24".

mattkevan• 10 years ago

One of the first Macs I ever saw back in the early 90s had a Radius pivot display which could be switched between landscape or portrait.

As it was mostly used for DTP it made loads of sense.

to3m• 10 years ago

I've got 3 Dell 24" monitors that can be used in portrait mode. (U2412M - 95dpi 1920x1200 eIPS - not expensive. But many Dell monitors come with this sort of stand.) When I had a desktop PC with 2 GPUs I had them lined up that way in a row. It have to say it was a bit menacing at first - it's about a 48" diagonal. But, you know... you make do. I took a few pictures at the time but the only one I've got handy is it running Doom: http://ffe3.com/pics/.3monitors/IMG_1327.JPG

In the end I missed the horizontal space often enough that I've now settled on having at least one full-size - i.e., not laptop display - landscape display in the setup. (Currently I've got my laptop, 1 x landscape in front of me, and 1 x portrait to the side.)

If you're going to do this, I guess you want to buy IPS-type monitors to minimize colour discrepancies due to the wide range of viewing angles you'll be using. eIPS is supposed to have a 170° viewing angle, but the colours on mine still aren't quite consistent from side to side (or top to bottom as it is once rotated). If you've got a TN-type display I imagine it will be even worse.

Also might be worth buying all your monitors at once. I bought mine over a couple of years; the colour temperature is very slightly different on each one, even when using the factory-calibrated settings, and one has a noticeably different anti-glare coating.

e12e3• 10 years ago

At some point (I believe Windows 7), Windows started allowing the use of ctrl-alt-arrowkey to rotate the display. I think it depends a bit on the graphics drivers, but I also think most "standard" drivers (ie: Intel, Nvidia, AMD) supports it out of the box. It can be a bit confusing if you hit ctrl-alt-downarrow (invert screen) by surprise... (ctrl-alt-uparrow is the shortcut for standard mode).

Aloha3• 10 years ago

Those CRT Monitors are probably the weakest part of the system in terms of durability.

krylon2• 10 years ago

Total envy! There is an Alto in the Heinz-Nixdorf-Museum, but it is not functional.

Seeing one of these machines in action would be awesome. (Is there an emulator available?)

kens12• 10 years ago

The Living Computer Museum in Seattle has a running Alto, but I haven't seen it. I've used the Salto emulator: https://github.com/brainsqueezer/salto_simulator

Aloha3• 10 years ago

I have seen it, and used BravoX on it. I even gave a demo to standers by once I figured it out. Its a very interesting system, one that is clearly not too removed from a modern word processor.

EvanAnderson• 10 years ago

This emulator looks interesting: http://toastytech.com/guis/salto.html

pjmlp6• 10 years ago

This was a great system.

The more I research into Xerox's papers and manuals for Interlisp-D, Smalltalk and Mesa/Cedar systems, the more I become convinced it was a big step back to the industry the adoption of inferior systems like UNIX.

Thankfully many traces of those ideas are now in Windows, Mac OS X, Android and iOS, Language Playgrounds and many IDE workflows.

Joeri• 10 years ago

Mass market products are rarely best in class, they are all about offering 'good enough' at commodity prices. Unix won because it was cheap, widely available and got the job done.

kens12• 10 years ago

The famous article "The rise of 'Worse is Better'" describes the victory of Unix/C over the "right thing" style of design : https://www.dreamsongs.com/RiseOfWorseIsBetter.html

Edit: I've changed the link. Thanks for letting me know about the bad redirect, golergka. The jwz link looked fine to me; it's pretty obnoxious if the site does a NSFW redirect.

zackmorris• 10 years ago

I agree. UNIX has some brilliant ideas, like isolated functions (executables) connected by streams, but beyond that it made a lot of mistakes that we are still dealing with today.

The biggest one being a C-centric view of programming that has cost the world untold billions of dollars when dealing with untrusted data. It could have used a statically analyzable functional middleware of some kind, falling back to micro optimization only when needed - the way that Clojure works with say, JavaScript.

The other major failing that I see is overlooking ideas from ZFS, that the filesystem can act as a virtual tree over any storage medium, so UNIX wastes a lot of time on things like dependency hell, permissions, and distinguishing between file and socket streams or local and remote processors. It could have jailed each process in its own sandbox where copies of libraries are reference counted by the filesystem, running in a virtual storage and thread space. We're just now seeing the power of that with Vagrant and Docker (technically it took so long to get here due to virtualization resistance by Microsoft and Intel).

My other main gripe is more about approach than technology. UNIX (and LINUX especially) stagnated decades ago due to the RTFM philosophy. The idea being that to be proficient in UNIX, one had to learn the entirety of the operating system. This goes against one of the main tenets of computer science, that we are standing on the shoulders of giants. So I really appreciate how passionately the Alto tried to make computing and programming approachable to the masses.

I keep hoping someone will release a portable lisp machine that can run other OSs under virtualization and release us from these antiquated methodologies..

jacquesm3• 10 years ago

The biggest one being a C-centric view of programming that has cost the world untold billions of dollars when dealing with untrusted data.

That's pretty simple to explain: all those other options were just way too slow to get the kind of performance required out of the hardware available at the time. The difference was simply too large to be ignored.

It's all nice and good to theorize about how the past should have been, but without UNIX you probably wouldn't be writing any of this on the medium you're currently using.

It has its flaws and it is far from perfect but at the time it fit the bill nicely.

The real problem is that we are categorically unable to move on when better options are around. There is a large amount of silliness involved when it comes to making responsible choices in computing, lots of ego, lots of NIH. Those are the real problems, not that UNIX was written in C.

digi_owl9• 10 years ago

Err, are we not taking things out of historical context?

dave2000• 10 years ago

The biggest one being a C-centric view of programming that has cost the world untold billions of dollars when dealing with untrusted data.

I'm not sure it cost anyone anything. I mean, a lot of the OSes were/are written in it, so if you were going to go down that path you'd have to not totally forget to add a rather large benefit in the credit side. It's hard to imagine but programming wasn't always about compensating for not quite understanding how the 17 different frameworks you've downloaded from github and dragged into an IDE worked by just getting a faster machine. Once upon a time people had to carefully measure how much to unroll the loop, or how small a lookup table they could get away with before the errors become a problem.

gumby3• 10 years ago

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-centered, IO-focussed machine which was super radical for its time. If you wanted to do a lot of computation you could steal cycles from the screen update, causing it to go black (in just the bottom half or so IIRC which I probably don't).

Error in the article: I do believe the Alto was the origin of the BITBLT instruction, but it was based on the PDP-10 (PDP-6) block transfer instruction BLT, and the expression blitting was current before the Alto was developed. In fact PARC had a PDP-10 which was the standard research computer at the time -- homemade as well (clones) because at that time Xerox was in the computer business and wanted PARC to use an SDS. (Again this is before my time though MAXC was still running when I was there -- with an Alto as its front end!)

Also contrary to what the article says, the Alto display was not unusual in being portrait mode -- most glass TTYs (think ADM-3A, Hazeltine, VT-52, and I believe the 3270 as well) were taller than they were wide, like a piece of paper. The Alto display was unique, as mentioned, by being bitmapped and black on white. Because of the Alto, bitmapped portrait mode was standard for workstations such as the CADR lisp machines, Bell's BLT terminal, three rivers PERQ, and of course the later PARC computers we used, Dolphins, Dorados (all ECL logic!), Dandelion (sold as the Star). I remember vividly the first landscape machine I used, the Symbolics 3600 in 1985. I didn't, and still don't appreciate the wasted space of landscape displays.

Three-button mice with the mouse buttons arrayed horizontally was also standard because of the Alto. The first time I saw the Macintosh mouse in 84 I was shocked: how could someone use only a one-button mouse? There was a lot of mouse (originally called the "bug") experimentation in the 70s on button count and layout.

The microcode of the alto was compatible with the DG nova as that was the computers used at PARC before the Alto was developed (before my time!).

edit: forgot to mention the origin of blitting.

kens12• 10 years ago

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 display over and over as they were being sent to the screen.)

I'm confused about your portrait vs landscape comments, though. The ADM-3A, Hazeltine 2000, VT-52, 3270, as well as Datapoint, Four Phase, Viatron, etc had a horizontal display, not a portrait display.

gumby3• 10 years ago

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 can see this reflected in Unix, and therefore in Linux: unix was developed for the PDP-7 (and later -11), a reimplementation of some of the ideas of Multics, which ran on a mainframe. So C's IO was "user mode" (I seem to remember a funny line in the original version, something like, "You mean you I have to call a function to do IO?") and the kernel had expensive, primitive IO capabilities and involved the CPU in everything. Well, there wasn't any alternative in the smaller PDP line (FWIW PDP-10 were larger machines than the -7 or -11, though only the later models had channel IO).

Memory mapped IO was not uncommon on minicomputers.

I'm confused about your portrait vs landscape comments, though. The ADM-3A, Hazeltine 2000, VT-52, 3270, as well as Datapoint, Four Phase, Viatron, etc had a horizontal display, not a portrait display.

I'm confused / unclear. Those terminals had more columns than rows, true, but the character positions were rectangular. So the ADM-3 and the Datapoint were rather square, actually, because TV tubes were squarish, not paper-like as I claimed. I think I biased my memory because I used a bunch of hacked terminals like AAA Ambassadors which could cram 80x48 rather than 80x24 and because of the rectangular characters were portrait-ish. Unfortunately it's too late to go back and edit my comment.

Someone2• 10 years ago

"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?

rjsw2• 10 years ago

Why reverse engineer anything ?

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

kps• 10 years ago

  > 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…

dang5• 10 years ago

(If you want to post a link to the comment you meant to reply to, we'll move it and delete this one.)

vram22• 10 years ago

Interesting about portrait mode monitors, and overall. Was the DG Nova the same machine mentioned in The Soul of a New Machine? Read it a while back.

kens12• 10 years ago

The Soul of a New Machine was about the 32-bit Data General Eclipse (1980), follow-on to the 16-bit Eclipse (1974), follow-on to the 16-bit Nova (1969), which provided the instruction set for the Alto. So not the same machine, but related.

(I find the Nova instruction set strangely similar to the ARM in many ways, but maybe I've just spent too much time looking at the ARM1.)

Animats4• 10 years ago

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 control-Z, then the formatting info. The compiler stopped at control-Z. So you could use bold and italic in your programs, and make the source code look good.

As in the picture shown, the Stanford machines had the keyboard and display on top of the computer. This isn't required, and it's really annoying to type on. The keyboard is great; it's a massive casting around clicky keys.

Altos talk PUP, Parc Universal Protocol, over 3MB coax ethernet. Stanford had gateways to connect this to the wider world.

I think I still have some of the Alto manuals.

The vision statement for the Dynabook is in "Personal Dynamic Media"[1] This is worth re-reading every few years.

[1] http://www.newmediareader.com/book_samples/nmr-26-kay.pdf

Animats4• 10 years ago

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.)

eschaton• 10 years ago

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

theoh2• 10 years ago

Maybe Modula-3 is too distant from Mesa to make this a valid point, but if not, there's a discussion to be had about why the Mesa-influenced Modula-3 (or the arguably essentially similar Ada) didn't sweep all before it in the 90s.

Is it that the "small set of sharp tools" provided by C, and the "safe and somewhat onerous discipline" provided by Modula-3 represent two points on an evolution that's converging towards the ideal systems programming language? Or maybe the language level is the wrong level at which to be considering this, as if we were analyzing prose at the level of phonemes?

aswanson• 10 years ago

Wow. Please conserve and write down what you have. Pivotal piece of computing history.

dang5• 10 years ago

We've all been fans of Ken's blog for years, so were thrilled that he took an interest in this project. Not only is Ken doing these amazing writeups, he gathered together the master restorers and engineers, some of whom worked on Altos at the time, who are now working on this one. Seeing them set to it, inspecting the Alto and figuring out what would be needed, was a lesson in self-organization. It was an honor to watch from the side.

We have two goals. One is to have the restoration chronicled as it goes along, in a way the HN community can discuss and participate in. Obviously we hit the jackpot there, with one of the best technical bloggers in the world.

The other goal is to do something with the Alto that the community will find interesting once it's running. A couple ideas are to make it fetch and render the front page of HN (we'd happily write whatever code was needed to serve it in a suitable format, since HTML is probably a bridge too far), or if we could find a second Alto to communicate with, play Maze War on them (http://www.digibarn.com/collections/games/xerox-maze-war/#ma...). But we'll be eager to hear any suggestions the community comes up with!

ScottBurson3• 10 years ago

I have a Symbolics XL-1200 that I've been wondering what to do with. Would YC like it? It worked the last time I turned it on, but that was 4 or 5 years ago, probably.

It's like triple-pizza-box size, not a refrigerator nor even the size of the Alto.

rjsw2• 10 years ago

Wasn't the pizza-box one the XL-1201 ?

dang5• 10 years ago

I think the answer to that is very likely: hell yeah! But we should wait until the Alto is running. Can we keep in touch about this?

progman2• 10 years ago

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 (with TFT as screen) would make less effort than the famous monster 6502 which was presented recently.

abritinthebay• 10 years ago

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

orionblastar• 10 years ago

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.

kens12• 10 years ago

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

Aloha3• 10 years ago

LCM built MASSBUS adapters for their PDP-10's, its probably possible. (to be clear, the ALTO was built in total from COTS parts, the disks are of a known type used on many other minicomputers, including I believe the DG NOVA)

progman2• 10 years ago

Thanks to all the posters here for their answers and recommendations!

kabdib• 10 years ago

We had some Altos (and a laser printer) at the Bureau of Standards, when I interned there in the late 1970s and early 80s. They had a number of games; one of them was written in SmallTalk, which you could break into, and then muck around in. Some screenshots from BYTE and a few papers gave us syntax hints, and we were off.

At one point we had some questions about SmallTalk-76 and called up Xerox PARC. Managed to get hold of Adele Goldberg, who answered our questions but was not terribly amused. I think Alan Kay would have been friendlier to us kids :-)

protomyth4• 10 years ago

There are so many points in the computer industry where one or a small group's decisions changed everything. After listening to "Dealers in Lightning" you wonder about quite a lot of decisions. One of the later ones got me to thinking, what would have happened if Xerox had not got rid of its pre-IPO Apple stock and allowed the Lisa team to license Smalltalk? I wonder the sequence at that point with the Mac.

jecel4• 10 years ago

Xerox did license Smalltalk-80 to Apple. It was one of the products promised at Lisa's launch, but it was never delivered. It was ported to the Mac and became available to registered developers (I got version 0.7 through a friend who was a developer). In 1996 this evolved into Squeak and Apple was able to release it as free software thanks to its license from Xerox. Some people complained about the Squeak license, so in 2006 Apple re-released its part of Squeak under the Apache license (and the rest was re-released under the MIT X11 license by each part's author).

Xerox gave the same license to Tektronix (which launched its 4404 and 4406 Smalltalk computers), HP (which created Distributed Smalltalk) and DEC. The DEC license was extended to UC Berkeley.

protomyth4• 10 years ago

According to 'Dealers in Lightning' they did not license it when Apple asked the first time. They did when they licensed it to everyone else. This was all pre-Squeak.

fabled_giraffe2• 10 years ago

The original Macintosh really seems like it borrowed a lot aesthetically, in addition to the similarity in operation:

http://lowendmac.com/1984/macintosh-128k/

http://www.righto.com/2016/06/y-combinators-xerox-alto-resto...

protomyth4• 10 years ago

Well, Xerox got pre-IPO Apple stock, so I would hope Apple got something for the money.

kens12• 10 years ago

I'm not seeing the aesthetic similarity between the Mac and the Alto, except that they're both beige, have a mouse, and are taller than wide. What specifically do you see in common?

fabled_giraffe2• 10 years ago

Monitors back then were wide then and the Alto turned the screen on its side. The Mac somewhat similarly had a screen that wasn't wide. The Mac mouse is also copied from the Alto's if you look at the shape.

acd• 10 years ago

Did the Alto have a graphical chat system?

kens12• 10 years ago

As far as I can tell, no. The Alto had a program called Chat, but this was more like telnet/ssh, allowing you to connect to a remote computer, rather than communicate with a person.

kilroy123• 10 years ago

My uncle worked at PARC when this was being made. I probably wouldn't of gone into tech, if it weren't for him.

This makes me want to message him and ask him about his time there.

fernly• 10 years ago

get him in touch with the restoration group!

dang5• 10 years ago

Please do, and let us know what he says!

intrasight• 10 years ago

Xerox Alto brings back some memories indeed. I used one at CMU as a frosh to do engineering drawings for the Terragator (http://gizmodo.com/5072167/25-years-of-strange-and-wonderful...). Being new to computers, I didn't really get that a mouse and GUI were revolutionary. It just seemed so obvious. But that is the beauty of innovation done right - that to users it just seems obvious and natural.

e12e3• 10 years ago

The disk drive at the top of the cabinet takes a removable 2.5 megabyte disk cartridge. The small capacity of the disk was a problem for users, but files could also be accessed over the Ethernet from file servers.

(...)

The Alto was introduced in 1973.

2.5 megabytes of removable/swappable storage ? In the 70s? I'm amazed that users found it constraining! That's more than even the Amiga managed to fit on 3.5" floppy disks (Unlike the PC which generally were only able to format for 1.44 MB, the Amiga generally fit ~1.8 on the raw 2MB HD 3.5" floppies).

pjmlp6• 10 years ago

As Alan Kay states on his talks, for doing this type of research one needs to imagine how the hardware will look 15years from now and build such hardware, regardless how much expensive it might be.

dang5• 10 years ago

This point is so important that Alan has emphasized it as one thing we're mostly missing.

The Alto was not meant to be a personal computer but a "personal supercomputer"—hardware so far ahead of the curve that it could run the software of the future. In other words, not a personal computer but a machine for inventing personal computing with, which of course they proceeded to do. Having such hardware is what makes it possible to figure out what the software of the future needs to be. If you can't run it, you can't create it.

For me this sheds light on a couple of Alan's famous lines: that the best way to predict the future is to invent it, and that people who are serious about software need also to be serious about hardware.

Such advanced hardware is necessarily costly but should still be within the reach of a properly funded research lab. It seems to have been an enormous frustration to Alan and his colleagues that they were unable to persude hardware vendors to make such hardware at any price, especially the Alto's microcode-driven style of hardware. Among other things, that was what had enabled the PARC researchers to make the most of the limited memory they had, since when a task was consuming too much memory they could implement it in microcode, pushing it down to the hardware (at least from the software's point of view) and freeing up RAM for software.

kens12• 10 years ago

Keep in mind that although the Alto disk is removable, it is a hard disk, not a floppy; the user normally kept it mounted for a session, rather than using a new disk every time they load something. Thus, the disk needs to hold everything you need. (Although you could access files over the network with FTP.)

The user guide describes in great detail [1] why Alto users found 2.5MB of disk limiting. To summarize, the disk starts with 4800 512-byte pages. Basic OS stuff takes 900 pages. FTP and the editor take 900 pages. Fonts take more, as well as other commonly-needed software. So a non-programmer's disk typically has 1600 pages (800kB) available to work with. Programmers require more tools, so the free disk space is tighter. It seems people ended up needing to manage their disk space closely, even though 2.5MB sounds like a lot.

[1] See pdf page 20 of http://bitsavers.org/pdf/xerox/alto/stanford/StanfordAltoUse... for a discussion of why disk space on the Alto was rapidly used up.

e12e3• 10 years ago

I see. That coupled with the limited RAM (as opposed to eg: the Amiga 500 which had 512Kb), or the Amiga 2000 which had at least a full megabyte -- I think ours had 4MB does make a big difference.

Interesting to note (as @pjmlp mentions) that 1973 + 15 years leaves us at around the time the Amiga 2000 was introduced. I remember ours (a model b IIRC) initially had a 20MB hard-drive, later upgraded with another 40MB for a total of 60MB of storage. It could fit almost all of my floppies on there!

Looking at the wikipedia page for the Amiga 500 I see the RAM latency listed as 150 ns. I'm not sure if that's the actual latency to read data from RAM - if so it's within an order of magnitude for accessing RAM today! (I'm also a little sad that while my i7 is a lot faster than that ageing 68000 that ran at 7.5 Mhz, it's still not easy to find a single core with 7.5+ Ghz of performance :-( ...).

pmarin• 10 years ago

The restoration is also being documented in Marc's youtube channel.

https://www.youtube.com/user/mverdiell

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

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