HN Theater @HNTheaterMonth

⬐ fhood

I was disappointed that there was no mention of "happy capacitors". Consistently one of my favorite parts of these videos.

⬐ teh_klev

This brings back some memories. When I was a young trainee engineer back in the mid 80's I worked at a Data General (DG) broker/repair shop.

One common job we did was refurbishment of DG Phoenix and Gemini drives. We sometimes had Diablo's, which is the drive make in the Alto video (possibly a model 30) and Zebra units (these were monster multi-platter units).

The ones I worked on were the Phoenix and Gemini drives (models 6045 and 6050) and were known as 5+5's (MB's) and 10+10's (MB's) meaning that they had a fixed platter, usually carrying the OS and you could top-load a single platter cartridge. There's quite a good picture here with one of these drives in the drawer out position :

https://en.wikipedia.org/wiki/File:Data_General_NOVA_System....

There was a plastic lid you'd put on top of the cartridge which is why you can't see the cartridge release handle in that picture. Normally you wouldn't be able to spin up the disk unless the chassis was pushed back into the rack, however the spring loaded "drawer open" sensor switch could be pulled back a notch towards the rear of the rack so that you could start the drive for service/repair work.

We used to do head replacements, re-alignments and fix head crashes. As was mentioned in the video, so that you could ensure that a cartridge could be reliably used across different disk drives you had a special disk that contained servo tracks which you would align the heads with. I think there were two, possibly three servo tracks on this disk (my memory is a bit vague). There were test points on the electronics you'd hook a scope up to so that you could check the alignment - there would be various pot tweaking to get things just right. Once you thought you had things "just so" the next step was to run the exerciser tests from DTOS (Diagnostic Tape Operating System - yes we booted the diags from tape) or ADES (Advanced Diagnostic Executive System). The Gemini and drives also had these huge linear motors that when in full test mode (seek tests in particular) were quite scary things to behold. This video gives you sort of an idea:

https://www.youtube.com/watch?v=qZsHTWiI0-4

We used to do regular trips from Scotland to London with a pair of Phoenix or Geminis in the company Sierra estate (1st generation). These things were so heavy that you really had to think about your braking distance once up to speed :) That poor car eventually had to have its chassis around the tailgate re-enforced after a few years of battering up and down the motorway with all that big kit in the back. Fun times though.

⬐ agumonkey

When computer looked like car parts. I wish I could go back to 79 with a pi zero and a 128GB microsd and let PARC guys faint.

⬐ digi_owl

I can't help but wonder if we have lost more than we gained.

⬐ agumonkey

Spend most of my days thinking just the same.

⬐ martin1b

Since Alan Kay has been on HN recently, would love to hear his comments on the development of the Alto, some of the issues they ran into, how it was conceptualized and the real story of the Xerox board's misunderstanding of what it was.

⬐ jefurii

Is there a text link for this? Video is such a slow medium.

Edit: By this I mean that I can assimilate text faster than an equivalent amount of info delivered in video form.

⬐ kens

I've been writing blog posts on the Alto restoration (at righto.com) but they run a few days behind the videos.

⬐ jefurii

Thank you for that, I really appreciate the effort that goes into writing these posts! Great job on the project!

⬐ fit2rule

This is a wonderful project, and definitely very interesting .. although the careful, snail-like pace of restoration is frustrating, the results are going to be quite rewarding.

[spoilers]

Does anyone know - does the Alto need to be booted from disk, or does it have a PROM loader, or some such thing as onboard firmware to do the boot loading - like, is the problem possibly that there is "no OS" on the disk, and they have to work out how to put it on there, or is this not booting due to some other logic-level problem, i.e. something wrong with the boards?

⬐ gattilorenz

Looking at [1], it would seem they actually need a bootable drive. Knowing what's on the drive... well, that's another story.

Interestingly enough, the Alto could also boot from the network [2], but I guess it would just be easier to take a bootable drive and copy it to the drive. Even creating a whole disk emulator would probably be easier than netbooting an Alto these days. Bootable disk images do exist, as you can use them with the Salto emulator.

[1] http://www.righto.com/2016/06/restoring-y-combinators-xerox-... [2] http://history-computer.com/ModernComputer/Personal/Alto.htm...

⬐ fit2rule

Thanks for the info - very informative.

Seems to me that they might be better off doing a netboot at first, since this is the booting technique that requires fewer moving parts and less wear and tear on the disk drive .. but I wonder if they did netboot, would they have everything onboard that they need in order to format/configure the disk drive for disk booting, next? So many questions .. I guess I should spend some hours with the Salto simulator, which seems like a guaranteed enjoyable waste of time! :)

⬐ gattilorenz

The problem is, what do you netboot from?

Netbooting a modern computer from another modern computer is somewhat easy, but with old computers it can be a nightmare. I tried to boot OS9 on a G3 iMac from a 2012 Intel MacBook, and despite days of work I couldn't do it.

⬐ fit2rule

Wouldn't it be that the Alto uses normally available standard netboot protocols that could be set up easily with a Linux box somewhere?

⬐ digi_owl

Given that we are talking about a computer from 1973, the chance that there is anything "standard" about the network boot is minimal...

Edit: well damn, a quick search bulled up a lovely PDF from textfiles.com.

http://textfiles.com/bitsavers/pdf/xerox/alto/AltoBootProto....

⬐ gattilorenz

Cool! It seems most internet gateways contain a boot server, problem solved ;)

Seriously though, I would bet that, with enough knowledge & time, you might find everything you need to netboot an Alto here: http://xeroxalto.computerhistory.org/

/Ibis/AltoGateway/Servers/BootServer* looks promising

⬐ digi_owl

Yeah, still need to set up another computer on a ethernet (likely the good old thick coax kind with 75 ohm terminators) network that behave properly according to the pdf. Fun times...

BTW, if anyone wonders what pup stands for in that pdf:

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

⬐ kens

The main problem with booting the Alto off Ethernet is that it uses 3 Mb/s Ethernet, which is incompatible with "modern" Ethernet hardware. We can't just plug an Ethernet cable into the back of the Alto. Back then, Ethernet used a "vampire tap" that clamped onto a coaxial cable with spikes that pierced the cable to make the connection. And you could only make connections at special spots on the cable (marked with black stripes) in order to avoid signal reflections. https://en.wikipedia.org/wiki/Vampire_tap

The Living Computer Museum in Seattle is building a 3 Mb Ethernet gateway, which potentially would allow network booting.

⬐ yuubi

10M thick Ethernet also had vampire taps and cable (about 1/2 inch diameter) with marks on it.

⬐ digi_owl

Glad i got into networking at the tail end of the thin-coax era...