Is there anything wrong with USB card sharing IRQ's with other PCI cards??

[Calipso]

Hi, I was wondering whether or not having my USB card sharing IRQ's with other PCI cards can cause me any problems. I know that normally you shouldnt have IRQ's sharing. Here is the output of my /proc/interrupts file and let me know if its ok if I were to leave it like this.

CPU0
0: 130934 XT-PIC timer
1: 89 XT-PIC i8042
2: 0 XT-PIC cascade
5: 90 XT-PIC SoundBlaster
7: 0 XT-PIC parport0
8: 1 XT-PIC rtc
10: 4546 XT-PIC ohci_hcd:usb4, radeon@pci:0000:01:00.0
11: 665 XT-PIC acpi, ohci_hcd:usb2, ohci_hcd:usb3, uhci_hcd:usb5, uhci_hcd:usb6, eth0
12: 2 XT-PIC ehci_hcd:usb1
14: 10359 XT-PIC ide0
15: 1129 XT-PIC ide1
NMI: 0
ERR: 0

Currently my USB card is sharing one IRQ with my video card and another IRQ with my NIC.
Any comments welcome :)

[banzaikai]

You shouldn't have to worry too much. I was going to suggest enabling your APIC, but then I saw the specs in your tagline, and realized you probably don't have this feature.

As always (with me), some background:

Sharing an IRQ is like a phone with call-waiting. The thing rings (device requesting an interrupt), and you (cpu) answer. During the conversation (IRQ handler), you get another call (secondary IRQ). Depending on priority, you can click over to the new call, or just let them sit awhile. Thing is, some people (devices) don't like to wait, and hang up. This means you're (cpu) left wondering who (what) called.

A simplified way of seeing it, but it gets the point through.

Now, with PCI, they designed a way of assigning "sub-levels" to the IRQ priority (called "enumeration") that helps to offset this problem. It's kinda like having one of those "Merlin" type phones that can transfer calls and do voice mail an' stuff. For the most part, it does it's job well. Having too many devices on the one IRQ can cause a slowdown or mishandling if it gets too busy on the bus. On my boxes, the USB co-exists quite nicely with my video and ethernet (much like your config). It was when the sound card decided to hitch a ride on either of those IRQs that things got crazy. Just disabling my COM2 (ttyS1) freed up an IRQ for the sound to use, and everything's just ducky. I'd also suggest that to you, if you're not using either of the COM ports, disable them in your BIOS to free up IRQs 3/4 for the others to use.

So, if you're sharing (on XT-PIC systems) an IRQ with just one other device, it shouldn't matter too much, but when you start getting devices stacked up on one IRQ, things start going to heck in a handbasket.

banzai "NMI" kai

[Calipso]

Thanks for the reply. So far I havent had any problems with it. It seems like each individual USB port is assigned to an IRQ which I found kinda weird. I thought the card would just get assigned one IRQ and not each individual port. Anyhoo, since I havent had any problems Ill probably be leaving it the way it is. Oh and the specs in my signature need a little update. I now use a P3 900 that I got from my friend cause his room was kinda getting crowded with all his computers.