Monday, August 12, 2019

Fighting router's block

I've been quite busy at work -- you know, the thing that pays the bills -- so I haven't had much time to work on my hobby projects. When I have had time, I've found myself tinkering with small layout details and not making much progress in the routing of the board as a whole. I think of it as "router's block", akin to writer's block where you just can't seem to make much progress.

Rattling around in the back of my mind is still the question of how bad the clock distribution on my discrete component i4004 boards is. I'm hoping to find time to sit down at my electronics bench and really take a look at what the clock signals look like now. But how would I tell how adding a second (and, later, a third, fourth, and fifth) board would affect this?

Late one night it occurred to me that when I had the Instruction Pointer board fabricated I got two boards. The idea was to avoid a situation where I screwed up one board and had to wait for another to be fabricated and shipped from Europe, and it would serve as a reference if I wanted to check connectivity. Since the essential BSS83 MOSFET is no longer available I have little use for this second board. So why not use it to help test the clock distribution behavior!

All I need to do is mount connectors on this board and I have a ready-made second board to add to the board stack. Since I don't need this board to be functional, I can add whatever loads I might want to the clock lines and see what effects it would have while probing with my 'scope.

Now all I have to do is find the frelling thing. I've found the packaging these boards were shipped in (seven years ago!) but it's empty. I looked in all the obvious places for it, such as the box containing most of the components for this project, but thus far I haven't found it. This might actually be the incentive I need to properly organize my electronics lab.