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?
Interestingly enough, the Alto could also boot from the network , 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.
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! :)
The Living Computer Museum in Seattle is building a 3 Mb Ethernet gateway, which potentially would allow network booting.
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.
Edit: well damn, a quick search bulled up a lovely PDF from textfiles.com.
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
BTW, if anyone wonders what pup stands for in that pdf:
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 :
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:
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.
Edit: By this I mean that I can assimilate text faster than an equivalent amount of info delivered in video form.