more on a board | 6502 primer

Put sockets shoulder-to-shoulder. (You won't really be able to see the board material except at the edges.)

(This improves performance too, as connections get shorter, reducing inductance.)
Use DIP headers for some small parts. You can see a DIP header in the photo above, with all the colorful little discrete components on it.
Use pin headers for shorting jumpers for option selects, instead of DIP switches. You've seen these pin headers inside PCs:

You can see one in the photo above, although that one is for an IDC (insulation-displacement connector) to plug in a ribbon cable for a parallel printer.
PLCCs take less space than DIPs, but WW PLCC sockets are not cheap, and they have become difficult to find:

This is a picture of a 44-pin one I have from Berg Electronics, McKenzie Socket Division. These are no longer avaiable but you can get (Dec 2020) 44-pin Winslow ones at RS Online here, and 32-pin ones here. They're basically the same thing. Note that these do go into standard prototyping board with holes on .100" centers. I grabbed a tiny piece of cheap prototyping board to take this picture:

Jeff Laughton gives a couple of other ways to do PLCC WW sockets on the 6502.org forum at http://forum.6502.org/viewtopic.php?p=37202#p37202, and just a couple of posts down in the same topic, at http://forum.6502.org/viewtopic.php?p=37206#p37206.
If you lay out a PC board, use PLCCs and other SMT parts. They're not as hard to solder as you might think. Soldering SO and SOJ packages by hand does not require soldering one lead at a time. You tack two oposite corners, then starting at a third corner, just flood an entire side with solder, using a tip that covers two or three leads at once, leaving lots of bridges, then hold it vertically and go from top to bottom again with the iron, and all the excess solder comes off on the iron, leaving an even amount of solder on every pin, just right. It's amazing how easy it is. Extra flux helps, but then you might need a way to clean the resulting gooey mess off. I have a more complete description here (on the forum), and there's a picture two posts above that.
A few things like memories can be stacked since most of their pins are common and bused. Here are a couple of early examples I did with SRAMs in DIPs. The first one is four 512Kx8 SRAMs:

The time to do this is when most of the pins are common to the two or more ICs, as is the case with memory. Stacking them like this also gives the benefit of reducing the connection length and capacitance. There's more of a collection of this kind of thing in this forum topic. Some examples are extreme! :D
Narrower DIPs can be put under and inside of wider DIP sockets. If the smaller one is socketed (as it would have to be for wire-wrap), the inside socket's profile will need to be much lower than the outside socket's. Here's the idea, photographed from an old PC motherboard:
And as mentioned earlier, use serial-interfaced devices, particularly when maximum speed is not needed so they don't need to go directly on the processor's own buses. I mentioned the example of the MAX3100 UART which is interfaced by SPI and comes in a 14-pin DIP which takes far less room than the wide 28-pin DIP that the 6551 comes in. It's generally a little better anyway, with 8-byte transmit and receive buffers.

There's more about getting more on a (PC) board in the section, "What About Custom PC Boards?"

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last updated Jan 4, 2021