
Xerox Alto Restoration Part 3: drive ok and First boot attempt [video] - gattilorenz
https://www.youtube.com/watch?v=PR5LkQugBE0
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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-...](http://www.righto.com/2016/06/restoring-y-combinators-xerox-alto-
day.html) [2] [http://history-
computer.com/ModernComputer/Personal/Alto.htm...](http://history-
computer.com/ModernComputer/Personal/Alto.html)

~~~
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! :)

~~~
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](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.

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

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

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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....](https://en.wikipedia.org/wiki/File:Data_General_NOVA_System.jpg)

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](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.

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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.

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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.

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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!

