how many IRQ's do I have?

[chipbgt]

I was looking at my irq settings, and I had 15 irq's full..how many do I have total? Is this a system specific number or is it pretty much set for all IDE mobo's..the reason I ask is because I have a Asus P3bf with 2 hard drives, internal zip, cd writer and a dvd player already with a ide controller card that has three more slots, and I want to know if I can add anything else to it. need more info? let me know.

[JW310]

AFAIK, there are only 15 IRQ's available to use for all systems, regardless of setup.... so unless I am wrong (which is possible), you're going to have trouble adding anything else to your card.

JW

[Nathan]

The actual number is 16 IRQ's. You have to count the 00 too.

[chipbgt]

if I may borrow from a more popular thread,
hmmmmmmmmmmmmmm.

[JW310]

Thanks for the correction... yep, it's 16... thought 15 didn't sound right to me for some reason /forum/redface.gif


JW

[Nathan]

Well to add to your hmmmmmmmmmm... One time I was installing 98 on a new PC, I was adding devices, etc. Well I had run out of IRQ's. Oh great. That's a nice "Bonehead" move. So I decided to try installing this other device anyway just to see what error message would come up, if any. Well what happened was it took almost 10 minutes to boot up. But it did install the device onto another IRQ that was already being used. I forget what devices that were on it, but I thought this is interesting. It happened one other time too.

[socalgal]

The trusty PCGuide serves some good info.
http://www.pcguide.com/ref/mbsys/res/irq/func.htm

Go to Summary (on the left) for IRQ listing.

/forum/smile.gif

[This message has been edited by socalgal (edited 10-28-1999).]

[Nathan]

LOL, yea JW310. It took me a while to remember to count that one too.

[chipbgt]

I'm glad to get all this info..but now im just stuck I guess /forum/frown.gif do usb devices take up IRQ's? I woudl assume so...but if they dont I could always take out my two nic cards and plug in some external nics.

[JW310]

Let's see here... maybe I can get this one /forum/smile.gif... I believe that you just need 1 IRQ to use USB - the IRQ that's needed for the USB controller... you should be able to add USB devices with no problem!

JW

[awwall]

You must be able to use multiple devices on the same IRQ. Both by Audio board and Video board on IRQ 11. Windows apprantly had no trouble installing both to the same IRQ. Machine boots quick with little hesitation.

All of mine show used.

00 system timer
01 keyboard
02 programmable interupt controller
03 Com2
04 Com1
05 Modem
06 Floppy controller
07 Printer
08 Clock
09 Adaptec 2940 ScSi
09 IRQ holder for pci steering
10 USB
10 IRQ holder for pci steering
11 Audio Board
11 IRQ holder for pci steering
11 Video Board
11 IRQ holder for pci steering
12 Mouse(ps2)
13 Numeric processor
14 PCI bus master controller
14 Primary IDE controller
15 PCI bus master controller
15 Secondary IDE controller

[daveleau]

You can add many devices to USB w/o taking up IRQ's. The most profitable is to get a USB mouse. It will free up one. you can dissable com ports that are not in use too. I have 4 devices on USB and they would take up only one IRQ if thee wasn't a USB bandwith limitation of 12 MBs. I had to install another USB card to remedy that. It depends on what you want to hook to USB. You might look into trading that internal Zip for a USB version. It's even faster and it comes in either 100 MB or 250 MB. hope that helps!
Dave

[Livewire]

I think I have this correct. If not feel free to correct me. Two or more devices can use the same IRQ through PCI steering. There are two methods of accessing an IRQ they are level and edge triggered. Those devices that have an IRQ to themself are level, and others like hard drives can use edge triggered and share the IRQ. Thus giving you space for more devices than there are IRQ's --Livewire--

[blondini]

get a scsi card

[Underclocked]

What Livewire said /forum/wink.gif , BUT if you have more than two devices (and those devices must be capable of sharing an IRQ) on one IRQ, you will likely encounter problems.