Various different models, mostly classic series thinkpads. I can't be bothered to sell them for a few quid on ebay, they're not worth anything anyway, and you never know when they're going to come in useful. No company makes this kind of high quality hardware any more, including the modern lenovo thinkpads, so I'm hanging on to them; at least they don't take up very much space. And they all run freebsd! An 8-bit ISA bus dual 12-bit burr-brown DAC card for the IBM PC, designed by yours truly around 1986-7. This was a prototype, hand-taped 2-layer pth PCB, hand soldered. No CAD was used, the circuit was designed on paper and then the board layout designed on clear film with transfers, which was passed to the PCB shop to construct the board itself, which was a pretty primitive method even back then; we couldn't afford a CAD at the time (and software used to be expensive!). The board also had an 8-bit PIO port (the IDC socket), and featured its own local split-rail power supply using a DC-DC converter and low power voltage regulators, the board had to produce both +ve and -ve output voltages wrt ground. The two phono socket outputs were DAC-generated control voltages for another piece of equipment. I can't remember what the 3.5 mm jack socket was for. Those were the days; you would never get away with a pcb layout like that nowadays; well, I guess it's not too bad, too slow to worry about reflections etc. It all worked fine, amazingly enough. Sweet. That's similar to how I learned; the joy of actually getting the LEDs to light up in your pattern is like nothing else.
