Friday, June 3, 2022

20% through the second pass building the signals database


I had completed page 51 of the approximately 250 ALD pages by the end of the evening yesterday. That brought the count to 4,883 pin connections recorded. I might reach around 8,000 entries in the database at the completion of the project.

There are less than 12,500 possible signal pin locations in the two gate IBM 1130 I am restoring, but a full configuration machine could exceed 25,000 possible points. A gate holds three compartments (backplanes). Each backplane has 104 slots and each slot has 24 pins. Every slot uses four pins for power at a minimum when an SLT card is placed there, some spaces are taken with the core stack and not cards, although signal cables on the top and bottom edges don't need need to feed the usual power pins.  Thus, this is only an approximate count. 

You can't compare the two numbers, possible signal locations and captured signal pins, because there are probably duplicates due to the off-backplane cable lists I captured at the bottoms of ALD pages. These may reference some of the same pins that I capture as either outputs in phase 1 or inputs in phase 2. Connections that are solely within a backplane are more likely to be unique. I can do a detailed sort and look for and trim duplicates once I am done with phase 2. 

That will give me a more accurate sense of the fraction of all pin locations that are captured here. Another very important factor is that some card slots are empty in each compartment even for a fully configured IBM 1130 while others are empty when a particular machine does not have a feature or peripheral device installed. 

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