[ct-user] Keying from High IRQ COM Port?

[Tyler Stewart]

Usually, LPT1 will use IRQ 7 if it is set up in a bidirectional mode (SPP,
ECP, EPP).  This is necessary for some printers and for scanners and other
specialized hardware.  Otherwise it is not needed.  Soundcards or LPT2 if
installed tend to end up on IRQ5.  My favorites for COM3 and 4 if you have
enough IRQ's are IRQ 10 and 11.  IRQ 9 can sometimes be used, but like Bob
said, it is used to map the higher IRQ's to IRQ2 and sometimes it doesnt
work well as you are actually sharing the IRQ at that point.

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