How can I find out if a NIC requires its own unique IRQ or if it is able to share its IRQ with other devices?
I know that some devices can share their IRQ's while others can not.   The answer to this question will help me troubleshoot a problem I am having with my NIC.  The vendor's web site could not help me and their tech support is pathetic.  
I am using a Belkin F5D5000 NIC.
Thanks.  The advantage of PCI cards is that the IRQ issue is resolved automatically.  Are you TALKING about an ISA card?No, it's PCI.
I did not know that all IRQ conflict issues were resolved automatically.   Are you sure?   Is that true EVEN on and old Pentium 200MHZ PC running Win98se?

Can you provide a hyperlink to any resource that gives me the full details about this?   Thank You.  Patrick Rohan....Perhaps you would like to share the issue your having with your network adapter.

dl65  Certainly.  After I installed this Belkin NIC and rebooted a few times, I would automatically boot into Safe Mode.  When I removed the NIC, I was back to a normal boot.
On another occasion, when I reinstalled the NIC again and rebooted, AS SOON AS I connected the UTP cable from the NIC to my DSL modem, it went into Safe Mode again.  Once again, I removed the NIC to get back into a Normal boot.  

So this made me wonder if there was an IRQ conflict.  I looked at Device Manger when I first noticed the problem, but didn't see any exclamation points, which are supposed to be indicative of resource conflicts.  But, OTOH, i've also heard that D.M. does not always flag IRQ conflicts (My understanding is that if the device does not give correct resource requirements to PnP, PnP has no way of knowing that there is an IRQ conflict, and thus will not flag it as one.  Please expand on this if you can!)
The NIC was sharing an IRQ, since I have no free IRQs left.  

On the assumption that it could have been an IRQ conflict, I removed my modem, thus freeing IRQ3, which the NIC then used for itself.  After that, the Safe Mode boot up problem was resolved.   I don't need the modem anymore, so I can leave it out.  

But I'm still not quite sure if the cause of the problem was, in fact, an IRQ conflict.  I'd like to know for sure in order to improve my knowledge of how PC's work.  Is there any way to determine this?  One Belkin tech support person said that the NIC needs its own IRQ, but I can't really rely on that because their techs aren't very knowledgeable.

Somebody even suggested to me that the problem might simply have been that adding the NIC overloaded my power supply, which puts out only 200 watts.  This seems reasonable, since I have lots of devices connected to my PC.

If you could give me any advice on how one is supposed to troubleshoot problems like this, I'd appreciate it.  Thank You.  Certainly.  After I installed this Belkin NIC and rebooted a few times, I would automatically boot into Safe Mode.  When I removed the NIC, I was back to a normal boot.
On another occasion, when I reinstalled the NIC again and rebooted, AS SOON AS I connected the UTP cable from the NIC to my DSL modem, it went into Safe Mode again.  Once again, I removed the NIC to get back into a Normal boot.  

So this made me wonder if there was an IRQ conflict.  I looked at Device Manger when I first noticed the problem, but didn't see any exclamation points, which are supposed to be indicative of resource conflicts.  But, OTOH, i've also heard that D.M. does not always flag IRQ conflicts (My understanding is that if the device does not give correct resource requirements to PnP, PnP has no way of knowing that there is an IRQ conflict, and thus will not flag it as one.  Please expand on this if you can!)
The NIC was sharing an IRQ, since I have no free IRQs left.  

On the assumption that it could have been an IRQ conflict, I removed my modem, thus freeing IRQ3, which the NIC then used for itself.  After that, the Safe Mode boot up problem was resolved.   I don't need the modem anymore, so I can leave it out.  

But I'm still not quite sure if the cause of the problem was, in fact, an IRQ conflict.  I'd like to know for sure in order to improve my knowledge of how PC's work.  Is there any way to determine this?  One Belkin tech support person said that the NIC needs its own IRQ, but I can't really rely on that because their techs aren't very knowledgeable.

Somebody even suggested to me that the problem might simply have been that adding the NIC overloaded my power supply, which puts out only 200 watts.  This seems reasonable, since I have lots of devices connected to my PC.

If you could give me any advice on how one is supposed to troubleshoot problems like this, I'd appreciate it.  Thank You.  Have you tried installing it in another slot ? ?
Some devices do not like next-door neighbors...

patio.  What kind of machine are we talking about by the way?I did try another slot and that did not solve it.  
I have quite an old machine, actually.  It is only a 200MHZ Pentium, running Win98se.  It is a Micron and has 256MB of RAM.  Most irq are shared...........what was sharing the nic card....you have used the the msinfo command in the run box ?........your pc may under powered to handle new tech.....(200MHZ Pentium> i bet it worked ok on the dun with the 56k modem?merlin_2 wrote:
Most irq are shared...........what was sharing the nic card....you have used the the msinfo command in the run box ?........your pc may under powered to handle new tech.....(200MHZ Pentium> i bet it worked ok on the dun with the 56k modem?[/quote]

Frankly, I neglected to check what device was sharing the IRQ that the NIC was using.  All I know is that after one installation of the NIC, the modem failed to work, so presumably it was a conflict with IRQ3, which the modem was set to at the time.

I used msinfo only after I removed the modem.  Here are its results:
0   System Timer
1   Keyboard
2   Cascade
3   NIC
4   COM1
5   Sound
6   Floppy disk controller
7   LPT1
8   Real Time Clock
9   Video
10  Promise Card
11  WinTV and USB Host controller
12  Mouse port
13  Math Co-Processor
14  Primary IDE Controller and Bus Master IDE Controller
15  Secondary IDE Controller and Bus Master IDE Controller

merlin_2 wrote:
i bet it worked ok on the dun with the 56k modem?

I don't understand what you mean there.  

At the moment, I'm only trying to verify the following hypothesis:
Is it possible it could have been an IRQ conflict due to the NIC not properly communicating its requirements to the BIOS (despite the fact that Device Manger did not flag it as a conflict)?   Is that a logical hypothesis or not?Possible, but not definite. On those older model machines, IRQ'a were tight, and it wasn't that uncommon to be forced to choose between a sound card/modem/SOMETHING else all vying for the one open IRQ. Modems and onboard serial ports can share the same IRQ if both aren't trying to use it at once.Your THINKING is spot on.>>........but consider this>11irq?  WinTV and USB Host controller ............you may have excceded the irq usage.....for the system you have......

just like overloading a fuse box.......something has to give.....or have to be updated to make additions work./?GX1_Man wrote:  
On those older model machines, IRQ's were tight, and it wasn't that uncommon to be forced to choose between a sound card/modem/something else all vying for the one open IRQ.

OK.  So then the question becomes:   What is different about modern PC's that alllows IRQ's to be shared, while my older PC MAY not be permitting them to be shared?  Is it the BIOS?   Or is it something else?  

A google search quickly turned up these links that may be helpful. But briefly:

Unlike ISA and EISA cards, PCI cards do not select their own IRQ line. Instead they can only select one of four "interrupt pins", which are mapped by the motherboard chipset to IRQ lines. I'll stress this again -- only the motherboard BIOS knows how the INT to IRQ mapping is wired, and thus only the BIOS can change the IRQ mapping for the card. The IRQ mapping is usually configured at boot time by the PCI BIOS setup, with the the exact assignment ALGORITHM being BIOS-specific.


This link addresses in particular NIC issues:

http://www.homenethelp.com/web/howto/irq-sharing.asp


This is general Microsoft speak:

http://support.microsoft.com/?kbid=252420