Parallel port bandwidth

At one time I wrote a "PC logic analyzer", which monitors 13 input lines from the parallel port (two reads per sample) in a tight assembly loop to watch for a trigger condition, and then reads and buffers a whole lot of samples at a user defined speed in an equally tight loop. On most machines of 486 or better, the loop topped out at somewhere around a 500khz sample rate. This is entirely bus speed limited - some P4s do worse than some 486s. Thats a raw two-read tight loop with no handshaking - once you put some strobes and acknowleges in there, the actual throughput you will realize will rapidly drop. Dave -- dave06a (at) Dave Dunfield dunfield (dot) Firmware development services & tools: www.dunfield.com com Collector of vintage computing equipment: http://www.classiccmp.org/dunfield/index.html