Here is some potatovision proof of the AUI-hacked Farallon EtherMac AAUI #Ethernet MAU mentioned in this post working with #mTCP on an IBM PC/AT (with some help from an old Netgear twisted pair to WiFi adapter).
What I haven't done yet is verify that the AAUI connector still works, but I'd bet it does: all of its wires just pass through the board directly to the MAU.
Here is a wiring diagram if you'd like to try to hack up your own Farallon EtherMac AAUI MAU to work with AUI. It's not as simple as connecting the right wires together, since AAUI usually supplies +5V power while AUI supplies +12V. The answer is to use a voltage regulator to make +5V from +12V, or what I've used myself is a cool-running buck converter like the Recom R-78E5.0 series. I've used the 1A variant, not because the EtherMac consumes 1A (nowhere close) but because I have a bunch of these buck converters handy for various projects.
The diagram also shows capacitors connecting various "Shield" pins to ground. The standard defining AUI states that these pins must be "capacitively coupled" to Vc (which I've recklessly labeled GND) but offers no further guidance for the sake of non-wizards like me. I was not able to measure any capacitance between shield pins and Vc on a real MAU that I own, so I simply didn't fit any: the shield lines terminate on the PCB with no connection anywhere. AUI cables are allowed to be up to 50 metres long, and I'm guessing the coupling is meant to accommodate that. My ribbon cable is 5 cm long, so I'm guessing it does not matter.
