Missing PROMs? (was Re: Status)

Juergen Buchmueller pullmoll at t-online.de
Sun Jun 3 12:03:01 PDT 2007

Al Kossow aek at spies.com 
Sat Jun 2 13:38:25 PDT 2007 

> Juergen Buchmueller wrote:
> > Hi list,
> > 
> > my name is Juergen Buchmueller. I just subscribed this list, after I got
> > Eric's preliminary source compiled and running on my machine. Wow!
> Hi Juergen! If there are any bits missing, let me know. Eric has mentioned
> that I hadn't dumped all of the microcode decode proms, for example.

Hi Al,
long time no see & read! Well, as far as I can tell there _could_ be
another set of microcode proms, if you have an Alto II(XM). According to the
docs it isn't necessarily so. It depends on a chip on the control board.

Section 8, page 58 of AltoHWRef.part2.pdf says:
	Many Alto IIs have the 2K ROM capability but contain nothing in
	ROM1. In these Altos, the SWMODE operation is normally configured
	so that it behaves as if ROM1 didn't exist (i.e., according to the
	first table rather than the second). This is determined by the chip
	in position 51 on the control board. If it is labelled SW2K then
	ROM1 exists, but if SW1K then it does not. The alternate chip is
	kept in unused socket 76.

I can't tell from just looking at the microcode's disassembly, if another
set of PROMs should exist. You would have to look at your control board to
determine the status quo.

FWIW: I have a microcode and emulator opcode disassembler, and also an
(LALR) assembler for the emulator mnemonics, halfway working. I put a
Xerox Alto-WIP page at my home http://pullmoll.stop1984.com/alto/


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