IRQ1
0
IRQ 0
IRQ 1
IRQ or interupt request : An IRQ allows a device to request certain system resources on priority. Normally, the system allowcates the different non-competing IRQ numbers to different devices. The system allocated IRQs may some times be manually changed. However, it may lead to serious IRQ conflicts resulting in a hung operating system.
IRQ 0 - System timer. IRQ 1 - Keyboard. IRQ 2 - Cascaded signals from IRQs 8-15. IRQ 3 - COM2 (Default) and COM4 (User) serial ports IRQ 4 - COM1 (Default) and COM3 (User) serial ports IRQ 5 - LPT2 Parallel Port 2 or sound card IRQ 6 - Floppy disk controller IRQ 7 - LPT1 Parallel Port 1 or sound card (8-bit Sound Blaster and compatibles) IRQ 8 - Real time clock IRQ 9 - Free / Open interrupt / Available / SCSI. Any devices configured to use IRQ 2 will actually be using IRQ 9. IRQ 10 - Free IRQ 11 - Free IRQ 12 - PS/2 connector Mouse. IRQ 13 - ISA / Math Co-Processor IRQ 14 - Primary IDE. If no Primary IDE this can be changed IRQ 15 - Secondary IDE These are just a set of standard IRQs. For much more detail check our Ralf Brown's list located at http://www.cs.cmu.edu/~ralf/files.html
IRQ 3
The default IRQ for COM2 is typically 3, while for COM4, it is usually 5. These IRQ settings allow the operating system to manage hardware interrupts for the respective serial ports. However, these values can sometimes vary based on the system configuration and settings in the BIOS. Always check your specific system documentation for accurate IRQ assignments.
LTP1 should use IRQ7.
COM1-IRQ 4, memory addresses 03F8-03FF COM2-IRQ 3, memory addresses 02F8-02FF COM3-IRQ 4, memory addresses 03E8-03EF COM4-IRQ 3, memory addresses 02E8-02EF pg. 396
By default, the IRQ for the floppy disk controller is IRQ 6.
By default IRQ 7 is assigned to LPT1.
From: http://www.techadvice.com/tech/C/ComPort_TS.htmCom1, IRQ 4, address: 3F8Com2, IRQ 3, address: 2F8Com3, IRQ 4, address: 3E8Com4, IRQ 3, address: 2E8