IRQs, PCI and PCI-E and the A8N32-SLI

[evilharp]

Ok, here are the basics.

I have an A8N32-SLI and I was having a nightmare of a time trying to get my Audigy 2 to work without crashing. After much effort, and forum input, I was able to resolve the issue by moving cards around, disabling onboard devices/port (serial/parallel/1394/etc..), and reinstalling XP ( :disgust: ). I was able to get my audigy 2 its own exclusive IRQ (17).

Thinking everything was fine, I went about my business and enjoyed some games.

I was checking some settings (My Computer > Device Manager) and all of a sudden my PCI-E card (7900GTX), V.90 modem (PCI) and Audigy 2 (PCI) have the same IRQ address (18). Oddly enough, everything was stable and working. The weird thing is I didn't change anything on the system (software/bios/hardware) to provoke the change. Also, I have never seen a system that places 3 slots on the same IRQ before.

I reinabled the 1394 (out of curiosity) and now the modem and vid card are at IRQ 19 and the 1394 and Audigy are at IRQ 17. IRQ 18 is now unassigned.

My understanding of PnP and IRQ was that some are reserved (i.e. system timer - 0, keyboard - 1, CMOS - 8, ACPI - 9) and that the rest are assigned by FIFO (First In First Out). Any idea what the A8N32-SLI adheres to?

 

[grooge]

IRQ sharing.. if that is ok, don't worry. most HW is ok with sharing now.

 

[Peter]

All (!) PCI, AGP and PCIE hardware must (!) by definition of the standard, cope with IRQ sharing. This is a deliberate design feature of PCI, not a problem, not even a quirk or a performance issue.

Perceived "IRQ sharing problems" with modern (post-ISA) devices are and have always been driver bugs or similar things.

 

[evilharp]

Originally posted by: grooge
IRQ sharing.. if that is ok, don't worry. most HW is ok with sharing now.

True. But for some wonderful reason, Soundblaster (TM) cards are notorious for crashing systems if they cannot have an exclusive IRQ. This is apparently a common problem with "high bandwidth" devices.

Originally posted by: Peter
All (!) PCI, AGP and PCIE hardware must (!) by definition of the standard, cope with IRQ sharing. This is a deliberate design feature of PCI, not a problem, not even a quirk or a performance issue.

Perceived "IRQ sharing problems" with modern (post-ISA) devices are and have always been driver bugs or similar things.

Driver bugs? Creative products? Never!

Any suggestions for an equivalent sound product (mostly 5.1 gaming) that can match Audigy 2 in quality, but provide better driver stability.

 

[Peter]

That would be because media card drivers have always been notorious for drivers that work fine on the surface, but are severely lacking in their behavior toward the system - Creative's been particularly guilty of this. You noticed that already Support drones of those companies are also particularly guilty of spinning the "IRQ conflict" myth.

Consumer level soundcards aren't high bandwidth at all, btw. You need many many channels before you even come close to saturating the bus. They need fairly low latency response though, so if you have another card on the same bus that hogs the bus for extended periods, your soundcard will get hiccups. That's what I meant when I wrote about the delicate balance between fairness and throughput, over in the "why do people badmouth VIA" thread.

To my (limited) experience, and once again contradictory to said thread's title, I found that soundcards with VIA's Envy24 series chips work fairly well and with not nearly as many compatibility or driver quibbles as Creative's. YMMV.

Speaking of high throughput cards ... you'll be hard pressed to find a storage/RAID or gigabit ethernet card whose drivers can't handle shared IRQs or bandwidth contention. That's because that kind of stuff originally aims at the server/workstation market ... where customers don't routinely put up with crap that needs five months of driver updates before it starts working. Coming from the embedded/blade/telecomms arena, I've seen as many as 20 such devices (all ethernet/storage) share a single IRQ without any problem at all.

 

[evilharp]

Thanks for the input Peter. I'll look into Envy24.