Freaking IRQ's

[Flyboy]

I realize this is probably a newbie question, but oh well its late:

Since I installed my new Ultra100TX2 ATA/100PCI controller, my mouse will get all jerky periodically. I checked my IRQs and the controller was sharing IRQ14 with the ethernet card. The two cards were in PCI slots 4 and 5, which is shared on the P2B-F, so I moved the ethernet card to PCI #1. I reboot and the BIOS assigns it AND the videocard to IRQ 10. So I manually set the ethernet's IRQ to 14, but guess what? The Videcards IRQ followed suit and is also now sharing IRQ14 with the ethernet card.

How can I fix this? Slot 3 is free, but has a PCI fan in it that I use to cool the videocard so I hate to move it to that slot. No, I can't move the PCI fan card to slot 1 because there is not enough clearance. Here's what I've got:

P2B-F
AGP: Asus V7100 GeF2 MX400
PCI#1: 10/100 Ethernet (LinkSys)
PCI#2: Soundcard
PCI#3: OPEN (well fan is installed though)
PCI#4: OPEN
PCI#5: Ultra100Tx2 ATA controller

I thought about moving my old WD drive and CD-rom to the Ultra100Tx2 to free up the onboard IDE controller's resourses.

Here's the IRQ listing:
0 System timer
1 Standard 101/102-Key or Microsoft Natural Keyboard
2 Programmable interrupt controller
3 (free)
4 (free)
5 Win9x-ME Promise Ultra100TX2 (tm) IDE Controller
5 Intel 82371AB/EB PCI to USB Universal Host Controller
5 ACPI IRQ Holder for PCI IRQ Steering
6 Standard Floppy Disk Controller
7 ECP Printer Port (LPT1)
8 System CMOS/real time clock
9 SCI IRQ used by ACPI bus
10 (free)
11 Creative SB Live! Value
11 ACPI IRQ Holder for PCI IRQ Steering
12 PS/2 Compatible Mouse Port
13 Numeric data processor
14 Linksys LNE100TX Fast Ethernet Adapter
14 NVIDIA GeForce2 MX/MX 400
14 ACPI IRQ Holder for PCI IRQ Steering
15 Secondary IDE controller (dual fifo)
15 Intel 82371AB/EB PCI Bus Master IDE Controller

BIOS is set for NON-PnP OS.

 

[jlanka]

Here's the situation: IRQ sharing in this day and age is perfectly fine. It's called ACPI. No need to worry about it. Attack the problem from this angle:


Just find the slot combination that eliminates the mouse jerkiness (is that a word?) Don't worry about IRQ sharing.

<i>It's always the one thing you never suspected.</i>

 

[Flyboy]

Yeah, it seems to be better now the ethernet is sharing with the videocard. I knew that PCI PnP devices today are capable of sharing, but I was under the impression that you should try not to- especially with the videocard and soundcard. You think this will work fine then? I haven't tried online game performance. It seems like I may have problems here because the ethernet and videocard would be fighting for the bus.

 

[pat]

The cpu cannot answer more than one interrupt at time, so they wont fight, they will wait. If one card ask an interrupt, the cpu will check which one and give it the time it need.

-Always put the blame on you first, then on the hardware !!!

 

[jlanka]

Also, what OS are you running?

Anyway, I've got pretty much all my expansion cards on one IRQ (W2K) and I can play UT without so much as a hiccup. Believe it or not, it works.

<i>It's always the one thing you never suspected.</i>

 

[troopr]

Flyboy,

Becasue you have ACPI enabled, you wont have much say so in IRQ assigning. I had a similar problem and solved it like this: removed all traces of my sound, ethernet and modem. turned system off, physicallly removed all 3 cards, rebooted and installed 1 at a time trying difernet PCI slots until i had everything on a se[perate IRQ.

Also, if u disable "SB emulation" in device manager, it free up another IRQ.

Another thing, win2k and XP are designed to share IRQ's. but even so, because you have a less than cutting edge vid card, you might see several more FPS by having it on its own IRQ. If you had a GF3 card, it has plenty of oommph to share IRQ's and still perform without a hiccup.

Hope it helps and good luck

Joe

<P ID="edit"><FONT SIZE=-1><EM>Edited by troopr on 02/21/02 03:31 PM.</EM></FONT></P>

 

[Flyboy]

I'm running Win98SE. Thanks for the help guys. I know how interrupts work, but I guess what I'm not sure of is how two devices (PCI cards) share one IRQ. To me, it seems that it is better for every device to have its own IRQ and the IRQs should be assigned by the level of importance of the device. Anyway, the mouse isn't stuttering anymore, so things are good. Well- at least for now. If I can play multiplayer games without any problems, then everythings cool.

Thanks!

 

[Flyboy]

Thanks jlanka. Apparently your right. Things seem to be working now. Any idea how two PCI devices share the same IRQ? How does the processor decide which to service?

 

[Flyboy]

Becasue you have ACPI enabled, you wont have much say so in IRQ assigning. I had a similar problem and solved it like this: removed all traces of my sound, ethernet and modem. turned system off, physicallly removed all 3 cards, rebooted and installed 1 at a time trying difernet PCI slots until i had everything on a se[perate IRQ.

Hmmm. Maybe I'll try this then. Well first I'll wait and see if I have any problems with the current config.

I chose not to install the SB emulation to begin with, so that IRQ is already available.

I have Win98SE. I may try what you said, and also move my old WD hardrive and CD-rom to the new PCI ATA100 controller. Then I could disable both Primary and Secondary IDE controllers to free up more resources.

Thanks Joe!


EDIT: BTW, one thing that confuses me is why the system assigns sharing of IRQ's when I have THREE free ones? Why wouldn't it first attempt to assign every device its own IRQ before resorting to sharing??? WHY? WHY? WHY?
<P ID="edit"><FONT SIZE=-1><EM>Edited by Flyboy on 02/21/02 03:42 PM.</EM></FONT></P>

 

[troopr]

Hehehe, I cant answer why it makes em share IRQ's when there are free ones available. I've been told if you disable ACPI, u could cause some seroius problems that will make you seek pyschiatric help.

i dont know if u are aware of another resource that is very helpful. Heres a link:

www.motherboards.org

Joe

 

[Crashman]

I always disable ACPI on BX systems because the BX is not 100% compliant. In fact one of my boards (an Epox BX3) crashes constantly with ACPI enabled. ACPI doesn't seem to affect my SY-BA+III though. So it's hit or miss with ACPI on the BX.

What's the frequency, Kenneth?

 

[Flyboy]

QUOTE from <A HREF="http://www.homenethelp.com/web/howto/irq-sharing.asp" target="_new">http://www.homenethelp.com/web/howto/irq-sharing.asp</A>:

According to Microsoft (article here), placing your NIC in
PCI slot 1 is bad news. You will probably end up with a NIC sharing an IRQ with your video card. Symptoms: "Unable to browse network" messages when looking at your network neighborhood. Read the article for the fixes

Ummm....I guess I'm going to have to remove the PCI fan in order to move my Ethernet card...dangit!


EDIT: That article is probably old or something. I don't seem to have a problem sharing the IRQ b/w the vid and ethernet cards. So I'll probably just leave it.
<P ID="edit"><FONT SIZE=-1><EM>Edited by Flyboy on 02/22/02 02:53 AM.</EM></FONT></P>

 

[Flyboy]

Do you disable it throught the BIOS (checking manual now...)

I believe my ACPI is disabled already because I can manually change the IRQ assignments in the BIOS. I believe if ACPI is active, then you can't do this.

 

[Crashman]

Yes.

What's the frequency, Kenneth?

 

[Flyboy]

"Yes" to disabling it in the BIOS?
or
"Yes" yours is already disabled Flyboy because you can change the IRQ assignment in the BIOS?
or
"Yes" to both of the above?