Practically speaking, though, it's as much a computer as an Adaptec ISA SCSI board. True, both do have firmware and to have some sort of processor, technically making them a computer, the computer part is so embedded as to vanish from sight. And is a PU Type 2 (Physical Unit) in SNA parlance (as opposed to a Front End Processor (FEP), a PU Type 4, or a CPU itself, a PU Type 5). All have their own little dance to do in the grand scheme of things on an SNA network. First of all, only the voltages are ordinary (-/+12). It's going to be SYNCHRONOUS serial, meaning that the data clocks are on pins 15 and 17, with NO start bits, NO parity bits, NO stop bits, just 8-bit bytes, one after the other. SYNC comms get better throughput than ASYNC for this reason (8-bits vs 10-bits per byte). The Z8530 SCC chip can be made to do SDLC SYNC I/O. We used it on our SNA products. I used to make and sell HASP/3780/SNA boards for VAXen (I still have a bunch). I am here to tell you that while it _can_ be done, it's a major, major undertaking. Making 68000 boards that simulated a PU Type 2 (3274) was a significant commercial endeavor, 10 years ago. I worked on the guts of the code, on the application end, the device driver, all of it. I would _never_ consider re-implementing SNA as a non-paying project. In effect, your "drivers" would have to emulate a 37x5 FEP sufficiently enough to fool real Blue hardware. We had these HP line analyzers, I forget the number, with a 40-column screen and TU-58-sized tape drive. In addition to tracing traffic, you could write programs (subject to severe memory limitations) that could listen for some stuff on the line, respond appropriately and simulate portions of the data stream. We had one program that took two of us to write and debug that could lead a PU Type 4 (ours and a portable terminal called an Informer) through the login process, and that was about it. A connection and one data packet. With a better protocol engine (to properly keep track of RR numbers), it might have been possible to do more, but we maxed out the HP box. Let's put it this way, I'd put writing a driver (assuming you had a compatible SYNC serial port) to talk to a real 3274 and then to terminals, at least as complex as writing an implementation of PPP from scratch, possibly with TCP/IP thrown in on top, just to make it a little harder. SNA is extremely non-trivial. Just because it's classic, don't make it simple. OTOH, the 3274 is a nice, *portable* piece of commonly used Blue Iron that would make a fine addition to any collection. _Using_ it is a different matter entirely. -ethan