Alto II (was Re: PDP-8 prices

From: Derek Peschel <dpeschel_at_u.washington.edu>
Date: Mon Jan 25 23:08:28 1999

> The problem with the PERQ manuals was that they didn't explain things.
> They expected you to already know it, and just need reminding about (say)
> the microcode fields...

Weren't there documents that explained everything, but were internal only?
Of course that is a huge problem when companies go out of business.

> > If you look at the Alto manual, you can see Diablo's model numbers.
>
> ...which is a pdf file, which I'll have trouble reading...

hmm. I've never seen that info except on the one site. You may just have
to find a way to read those files.

I wouldn't say they're complete (especially by your standards), but they're
better than the information which I previously had, which is almost none.
So they're worth reading.

> All PERQ I/O is done in microcode as well. To give you some idea of what
> it looks like, here's some microcode to implement a centronics interface
> on the optional PERQlink port

> {Centronics driver microcode for standard parallel printer on the PERQlink}
> {interface.}

Why do I suspect the microassembler syntax was based on Pascal's?

(I had written "microsyntax" but that's not really the same meaning.)

> Am I correct that the Alto keyboard was scanned in microcode, and that
> selecting which file the machine booted from was done by holding down
> some of the keys during the boot (the 16 bit? number from the keyboard
> was ORed with the disk address or something).
>
> If so, then it was possible to have boot files that were almost
> impossible to boot from because of the keys you had to hold down. They
> were generally known as 'nose-boots' for the obvious reason.

Yes, you are correct. See my huge reply to Sam's small question ("Why not
just create a microcode emulator?").

Maybe they assumed you wouldn't need that many boot files anyway. Probably
several would suffice: the Exec (OS and shell), the Scavenger (disk repair),
the NetExec (Exec with network file capabilities), the FTP program, a disk-
creation and copying program. IIRC those were all available, and that's
about all you need, I think.

> Alas the PERQ makes it less fun. They keyboard is handled in hardware.
> You do select the boot image by holding down _a_ key during the boot,
> but it's only one key, so there's no problem.

:) You still have 50-100 options to choose from (one per key). That's not
as many as 256 (128? 65536?) but it's still a lot.

I wish modern machines had useful and flexible boot-time options. The IBM
RS/6000 does (but being IBM, everything is done with the function keys).
Other workstations do. Home machines don't, but their device interfaces are
so complicated that they should. The shortcuts on the Mac are a good start,
but I'm talking about documented, powerful, consistent firmware, to the
level of a mini-OS if necessary.

-- Derek
Received on Mon Jan 25 1999 - 23:08:28 GMT