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Thursday, July 11, 2019

What is the standard IRQ assignment for COM2?

What is the standard IRQ assignment for COM2?

  • IRQ 0
  • IRQ 7
  • IRQ 4
  • IRQ 3

What is the standard IRQ assignment for COM2?


An IRQ (Interrupt ReQuest) is a physical connection on the motherboard through which a piece of hardware communicates with the CPU and the OS; the CPU responds through an I/O (input/output) memory address. The so-called Standard IRQ assignments date back to the early days of DOS and Windows 3.x.
In the bad old days, IRQs had to be assigned manually, either by means of physical switches, jumpers, or with software. Even now, you may occasionally have to assign an IRQ manually, although it doesn't happen often. Also, newer computers have more than 16 IRQs and the hardware and software can share IRQs without fighting. Usually.
IRQ Assignment
0 system timer*
1 keyboard*
2 link to second IRQ controller*
3 serial port 2 (COM2; usually the modem, if present)
4 serial port 1 (COM1; usually the [serial] mouse, if present)
5 available, OR sound card (if present), OR parallel port 2 (LPT2)
6 floppy disk controller*
7 parallel port 1 (LPT1) = the printer
8 real-time clock*
9 available (may appear as IRQ 2)
10 available
11 available
12 available, OR PS/2 mouse (if present)
13 math coprocessor*
14 primary IDE controller (first/main hard drive)*

15 available, OR secondary IDE controller (other hard drives/CDROM, etc.)


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