3 ms·
MSDOS 3.3 had COM1, COM2, COM3, COM4, LPT1, LPT2, and LPT3. LPT4-9 and COM5-9 was not part of MSDOS.
by zaxomi 3y ago
MSDOS 3.3 had COM1, COM2, COM3, COM4, LPT1, LPT2, and LPT3. LPT4-9 and COM5-9 was not part of MSDOS.
- olyjohn 3y agoIIRC those were mapped to specific I/O and IRQ Ports back in the day. COM1: I/O port 0x3F8, IRQ 4 COM2: I/O port 0x2F8, IRQ 3 COM3: I/O port 0x3E8, IRQ 4 COM4: I/O port 0x2E8, IRQ 3 I also remember, there was a while where there was no IRQ sharing. So some machines couldn't use all the COM ports available. Or you'd add in like a modem, and would have to disable the onboard COM port if it was using the same IRQ.