System/1 Build Log

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An ongoing chronology of System/1's construction, and any other related musings.

14th June, 2014 - Populating the register file

This entry was backdated.

Having completed the wiring of the register file during the week, and performed a quick test to make sure power was getting to the right pins and the connections all buzzed out as they should, I figured it was about time I installed the logic chips and tested it out.

Ferreting through the big box of parts, the input data selectors, 4-to-16 decoder for the 'write' signal, and glue logic chips come to hand first, leaving just the two 1-of-16 output data selectors — and they don't seem to be here. A quick glance down the Farnell packing list shows they were definitely included in the order, so I check again and discover I overlooked them because they were in a bigger IC tube than all the other logic chips...

... which makes perfect sense, because they're packaged in 0.6" DIP instead of 0.3" DIP. Damn. Should have paid closer attention when ordering sockets for all these chips; at least I won't be making that mistake again.

After a brief break for some cathartic swearing, it's time to assess my options; rebuilding the board from scratch would be one, especially since I'm not especially happy with the connectors I chose for the individual register boards to plug into, but that would take a while and also risks leaving me with two useless boards if there's some hitherto unnoticed problem with the design. In the interests of making progress with the rest of the system and with testing, let's skip that option and find a way to bodge this one into working.

Some sort of adapter would be the obvious answer, although it will probably have to be a makeshift one; the commercially-available adapters appear to be symmetrical about the long axis of the package, which could make for a tight squeeze. There's just about enough space between the two sockets and their neighbours to accommodate the two 0.6" packages side-by-side, but if the bodies of the sockets on top of the adapters extend too far outside the package outline they could foul each other — and they're not cheap enough to let go to waste if they don't fit, either!

However, my brother is here for the evening and is manning the barbecue, so I'll worry about this some other time. Food seems like a better idea for now...