What is IRQ?

Question

What is IRQ and IO address? Whats the difference? are IRQ nos same on all motherboards? Where and how to change?

Answer 1

IRQ is an Interrupt Request line from the Intel Processor, or reserved Interrupt Request from an internal process. Many of these are assigned to fixed functions, so you do not want to write your software to use one of the RESERVED IRQs. An IO address is also an Intel Processor address assignment. Again, you would not wire to an address that is used by the standard PC environment.

There are hundreds of user definable IRQ and IO addresses... GO FOR IT.

Good luck and Happy Computing!

Answer 2

"In computing, an interrupt request (or IRQ) is a phrase used to refer to either the act of interrupting the bus lines used to signal an interrupt, or the interrupt input lines on a Programmable Interrupt Controller (PIC). Interrupt lines are often identified by an index with the format of IRQ followed by a number."

IRQ address references to a device or "software" which will request an interrupt to the normal routine onto the normal bus lines. Example, let's say you insert your USB device into the USB port. The USB port has an IRQ of 5 which allows to "stop/pause" the flow of the normal address bus (for regular stuff; hard drive, memory access). This has "higher" priority and therefore pauses and switches to do the task of putting USB device into the rest of operating system.
IO address or port addresses and references peripheral devices.
The last two questions are fairly open ended, so please see more detailed information in the below links.

Answer 3

IRQ is short for Interrupt Request
I/O is short for Input/Output Address

an IRQ is a prioritized means to get the attention of your computer's CPU for processing information. Every time a piece of hardware needs to connect to the CPU it needs to stand in line and wait for other pending requests to complete. However, not each piece is weighted equally. Those with a lower IRQ numbers have a higher priority and will be completed first.

Input / Output are memory address that are reserved for a particular hardware or software. It is the same principal as your mail address, each device needs a reference address to store data and be contacted for retrieval.

Regarding the consistant numbering scheme between motherboards for IRQs, yes for the most part they are the same. Legacy computers have IRQs from 0-15 and newer computer have a range up to 224. For example here is a list of common devices and their IRQ assignments for legacy computers to give you an idea.

IRQ0 – Intel 8253 or Intel 8254 Programmable Interval Timer, aka the system timer
IRQ1 – keyboard
IRQ2 – not assigned in PC/XT; cascaded to slave 8259 INT line in PC/AT
IRQ3 – serial port COM2 and COM4
IRQ4 – serial port COM1 and COM3
IRQ5 – hard disk controller in PC/XT; LPT2 in PC/AT
IRQ6 – floppy disk controller
IRQ7 – LPT1
Slave 8259 (PC/AT and later only)
IRQ8 – real-time clock (RTC)
IRQ9 – no common assignment
IRQ10 – no common assignment
IRQ11 – no common assignment
IRQ12 – PS/2 mouse
IRQ13 – math coprocessor
IRQ14 – hard disk controller 1
IRQ15 – hard disk controller 2

Now regarding changing them, both IRQs and I/Os you don't have to change normally because they are automatically allocated by the BIOS and your OS. Prior to Windows 95, this was not an option, so it was done manually. Today it is likely you won't have to do this unless you are using hardware or software that is rather outdated and cannot be reconciled by the computer.
But if you were to change them, most BIOSes would have a section that you can change them or reset current allocations. You can also do this in your OS. I haven't tried to do this in any Unix variantes but under Windows 9x to Vista this can be opened through Device Manager. Open Control Panel from the Startmenu and goto System Maintenance. Find System, a sub member of System Maintenace. This will open a box with Hardware tab that leads to Device Manager or has a link to Device Manager. Now you can right click the hardware devices and change its properties if it has the resources tab available.

Answer 4

IRQ, stands for Inner Ramdon Question, and no they are not the same

Answer 5

i was going to say you spelled IRAQ wrong.
but here are some links I found
http://en.wikipedia.org/wiki/Interrupt_request -- IRQ
http://en.wikipedia.org/wiki/IO -- IO