System/1 Build Log

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

8th June, 2014 - Full set of register module boards assembled

This entry was backdated.

Now that the main register file board is wired up, it needs some register modules to plug into it! So far I only have the two I populated back in April, and although they sufficed for making sure I was laying the connectors out on suitable spacings it'll be a bit hard to test the full functionality without at least a few more registers to play with.

Luckily the boards are simple enough and quick to assemble, so after getting into a rhythm it only took a couple of hours to finish the sixteen remaining modules needed to fully populate the register file board. The only slightly annoying part is an ill-considered footprint for the decoupling caps; I used EAGLE's default library part, which has a tiny annular ring around each lead. Larger ones would have made fitting the capacitors rather less fiddly; a lesson to bear in mind for any future through-hole boards I lay out...

Now that I have the complete set of modules assembled, it's time to plug them into the register file and see how it looks. The full assembly takes up slightly more vertical space than I'd anticipated — only on the order of 5mm or so, though — due to the right-angle pin headers on the modules not fitting fully into the sockets on the main board. Not sure how I messed that up from the datasheets, but looking at the rigidity (or lack thereof) in the resulting connection I'd have been better off moving the headers back onto the boards a short way so that the modules hold themselves upright against the socket bodies, rather than flapping slightly back and forth as I move the register file board. Oops. At least they don't fall out, though, so it looks like I got away with it this time.