Peter van Hoof wrote: > Actually .... I disassembled the print.exe of dos 6.0 today, just to > satisfy my curiosity (there is nothing much on the net about old > technologie) and print seems to use one of the oldest multitasking > mechanisms around (in dos and windows) the msdos multitask interrupt. > and this is timer driven Just another small part of the mystery of the PC. The printer port was fitted with an interrupt mechanism so that it could be efficiently interrupt driven. The interrupt mechanism has a tri-state gate so the interrupt can be shared. That is why it *is* usually shared or perhaps, subverted by the sound card on IRQ7. Because ... they never *used* it to efficiently drive the printer (I too have disassembled print.exe!). More silliness. (Older) network cards tend to be set to IRQ3 by default. WIN95 assumes this which is *totally insane*, given that all machines since it was introduced are (quite properly) fitted with *two* serial ports, the second of which is hard-wired to IRQ3, generally cannot be disconnected from IRQ3 even if the serial port is disabled (but *why* would you relinquish a serial port anyway?). This is because the IBM version of the serial port, like the printer port, *had* a tri-state gate on the IRQ line but no-one (well, certainly not ...) could write OS code to utilize it to share the IRQ so - manufacturers decided it wasn't wanted and designed it out. Consequently, you have to set the network card to use IRQ5, which is *why* you must use IRQ7 for the sound card. It's not so bad if you use a 16-bit network card and can use the higher IRQs, but WIN95 was too dumb to figure this out itself. That's why setting up PCs is a tricky business. You think it's all sorted nowadays? Maybe? -- Cheers, Paul B.