Saturday, May 27, 2017

Alto event planning, work on IBM 1130 panel upgrade and on disk tool


I attended a meeting today at Computer History Museum to discuss holding an event to celebrate the Xerox Alto and other innovations, leveraging a few restored machines and many of the people who made those inventions. We also had staff from the museum, both historians and the live event producers, plus Marc, Ken, Luca and me for our restoration team.

Some of the people at the meeting who worked on these systems at PARC and are going to help with the upcoming event: Chuck Geschke (co-founder of Adobe), Doug Fairbairn (a founder of VLSI Technology), John Shoch (former president of Xerox Office Products Division and venture capitalist).

A number of the current staff of PARC were there too and will be involved. We expect to have the Alto we restored, at least two Altos restored by Al Kossow, a networked link to an Alto at Living Computer Museum, and hopefully Bruce Damer's machine which we are attempting to restore.

I did some diagnostic work during the brief time we had at Marc's lab today. I found that my synchronization between the various state machines involved in writing was not working properly, leading to a sector with nothing but zero output bits

I attempted to read a cartridge that wasn't archived properly earlier, but all records of all sectors had checksum errors reported. I used a scope to capture sector 0 on read of the cartridge in question. The data appears properly formatted so the issue is some regression error when I updated my logic.


I thought I had everything placed properly, it routed successfully and I worked my way through the minor manufacturing issues, such as silkscreen component outlines touching via hole pads. I was almost done when I spotted two light positions whose components were swapped around - register 2 (Storage Access Register) bits 4 and 5.

PCB layout - some swapped components to be corrected
While I could swap the input signal wires, it ruined the symmetry of the trace lines and complicated that section. I therefore planned to move things into their intended place and manually draw the traces to connect it properly. As you can see from the picture, it is a very dense board where the parts barely fit in place. 

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