I don't think the RAND code had the non-blocking stuff; AFAICR, all it had was named pipes (effectively). Jack Haverty at BBN defined and implemented two new calls (IIRC, 'capac()' and 'await()') to do non-blocking I/O. The documentation for that is in the 'BBN' branch at TUHS: http://minnie.tuhs.org/cgi-bin/utree.pl?file=BBN-V6/doc/ipc/await http://minnie.tuhs.org/cgi-bin/utree.pl?file=BBN-V6/doc/ipc/ipc My memory might be incorrect, but I don't think it was asynchronous (i.e. a process issued a read() or write(), and that returned right away, before the I/O was actually done, and the system notified the process later when the I/O actually completed). I actually did implement asyn I/O for an early LAN device driver - and just to make it fun, the device was a DMA device, and we didn't want the overhead of a copy, so the DMA was direct to buffers in the process - i.e. 'raw' I/O. So that required some major system tweaks, to keep the process from being swapped out - or moved around - while the I/O was pending. I found it on the dump of an MIT machine, but it was never run on any machine at MIT - we just had the source in case we had any use fot it. Noel