IRQ Conflicts

[gmgq]

Are there ANY mobo's out there that don't have IRQ sharing problems?

Nowadays, mobo's have up to 6 PCI slots, but what good is it if you can't successfully use them by just plugging in a new PCI card wherever you want, whenever you want?

I mean, how do IRQ's work? Aren't there like ~15 IRQ's at our disposal? Surely that should be enough for 6 measely PCI cards...?? Then why must some cards go for the same IRQ? There's plenty to go around.

I dunno, I've lived with swapping around cards and such for many years, but I'm just wondering why I should be dealing with those conflicts. You'd think that with all that plug&play mumbo jumbo that it would be smoother. Especially for users who aren't even aware of these problems, and go "doh, this new card I got is defective, better take it back."

[otheos]

Well PCI2.1 standard supports IRQ sharing so in theory you should be able to put any card you want in any slot and use it without any problems.

Now, you do have 15 IRQs but not all are availabe to the PCI masters. Things like the FPU unit need an IRQ not to mention the chipset etc.

Unfortunatelly poor stadard implementation can cause problems. Creative's SB Live for one is a card that can't stand IRQ sharing and most AGP cards don't like it either.

However most cards can happilly work (even SCSI cards with two IRQ's can share them with other high bandwidth cards -NIC). The problem then arises with the software implementation. I for one never liked MS's ACPI implementation and found myself wrestling with it more than once. Linux (2.4 kernel) on the other hand always worked and it seems to adopt the standard better (slight bias here so beware :)).

At the end of the day I end up planning where to put the PCI cards and try to avoid sharing IRQ's as much as possible. One thing I found out is that VIA chipsets don't like sharing USB and Sound Card IRQs! You can always disable unused hardware: COM ports, LPT port, PS/2 and USB are all there to disable if unused to gain the IRQs. Typically with an AGP, NIC and Sound card you only need 3 IRQ's so there you go, you can do it. Add an extra IDE controller, a SCSI controller (2 IRQ's for high end), a firewire card and you've filled them all, and if you run two printers (one LPT one USB) you have a ps/2 mouse and keyb but also a USB tablet, USB Zip, use your COM1 for external modem and COM2 for your calculator backup, then IRQ sharing is uanavoidable. With all the above hardware I can assure you all works fine in both W2K and RH7.2 Linux.

[jadison]

If you would, please take a look at the image I have below, this will help you understand IRQ's and how they are assigned.
This image shows how the IRQ's are configured on my system.

Long, but very descriptive explanation on IRQ's, Otheos. ;)

-=jd=-

http://neotech.8m.net/IRQ.jpg

[gmgq]

Yeah, I've disabled a lot of the COM ports and such that I don't use to free up some IRQs. But cards like the sblive can be a hassle.

jadison: oh yeah, I forgot about that other stuff. But there still enough IRQ's for the pci cards! ;)

[Axel]

here's a thought - perhaps you have too much junk on one box and should think about building a second one to move half the stuff to.....

Same thing with people who don't mind loading every program they get their hands on, but never even consider uninstalling anything because they still have room on their hard drive -

MADNESS!!! and just fishing for conflicts......

it's kind of like having a check-book and continuing to write checks because you still have checks.....

I used to think that I had to fill every drive slot in any case I had too - but have since gained my senses - and have enjoyed more uptime on my equipment.....

think about it -

[jadison]

here's a thought - perhaps you have too much junk on one box and should think about building a second one to move half the stuff to.....

was this directed at me or at gmgq...if it was me, I only plug in what I need: sound card, vid card, NIC, and modem.

excuse me if this was intended for gmgq

-=jd=-

[Mntsnow]

it's kind of like having a check-book and continuing to write checks because you still have checks

You mean I CAN run out of money before I run out of checks? DOH! Why didnt anyone tell me that before? ;)

[Socal]

No, Mntsnow, that's not possible. If you still have checks, then you still have money. :) It's called the "De Nile Check Method", and the inventor got rich holding workshops around the country. Works for me!

To stay on topic <g> here's a copy of my W2K IRQ assignments:

System Information report written at: 11/15/2001 04:58:36 PM
[IRQs]


IRQ Number Device
9 Microsoft ACPI-Compliant System
11 Matrox Millennium G400 DualHead MAX - English
11 Creative SB Live! Basic (WDM)
11 Symbios Logic 875XS|D, 2280X PCI SCSI Adapter
11 HP Ethernet with LAN remote power adapter
7 U.S. Robotics 56K FAX INT PnP
14 Primary IDE Channel
15 Secondary IDE Channel
8 System CMOS/real time clock
13 Numeric data processor
6 Standard floppy disk controller
4 Communications Port (COM1)
3 Communications Port (COM2)
1 Standard 101/102-Key or Microsoft Natural PS/2 Keyyboard

ACPI in action.

[Mntsnow]

Whew! I knew I remembered hearing that if I still had checks I had plenty of money!

[SalaTar]

IRQ Number Device
3 Microsoft ACPI-Compliant System
14 Primary IDE Channel
15 Secondary IDE Channel
7 VIA USB Universal Host Controller
7 VIA USB Universal Host Controller
7 SiS 900 PCI Fast Ethernet Adapter
7 PCI Simple Communications Controller
10 Multimedia Audio Controller
10 Multimedia Controller
8 System CMOS/real time clock
13 Numeric data processor
6 Standard floppy disk controller
5 ECP Printer Port (LPT1)
12 PS/2 Compatible Mouse
1 Standard 101/102-Key or Microsoft Natural PS/2 Keyboard

[gmgq]

Axel: Then why bother making motherboards with more and more PCI slots? Heck, why even bother having PCI slots when they could just include sound, nic and video built into the mobo?

These are EXPANSION slots, for future expandability. People buy these motherboards so that they have the option of buying more cards to upgrade their system. It wouldn't be economical for people to get a new tower, mobo, cpu, memory, power supply, etc. just to put their cards into in order to avoid IRQ conflicts.

I mean, my system runs very smoothly. It's not like I get BSOD or freezes every day. My system may stone on me perhaps once a month (and that's if I'm purposely fiddling with something). I'm just griping about the IRQ Conflict issue in general. Like others, I've had to deal with the issue over the years. So I'm just wondering why they haven't implimented it better. This is a very basic problem, yet not much has been done to resolve it. All they care about is making video faster, CPU's faster, hard drives faster, etc.

I'm sure MANY people are having various problems with their systems, and the root of the problem is probably an IRQ conflict -- yet they will probably never realize it. A game may lock up on them from time to time, or a particular piece of hardware may have occasionaly 'glitches' and require a reboot, etc. With the advances made in this technology, I don't see why we have to deal with these compatibility issues. Not everybody knows how to goto the device manager and check out the irq assignments, or look up which slots are sharing resources with other slots, or play around with the BIOS IRQ assignments, etc. It really takes someone who knows what they're doing to track down these conflicts. But unfortunately, those people are drowned out by others who don't know an IRQ from a BBQ.

For the record, here's what I have in my slots:

AGP: Geforce2 GTS PRO 64MB
PCI1: ATI TV-Wonder
PCI2: Adaptec 3port Firewire
PCI3: DLINK 10/100 NIC
PCI4: SBlive
PCI5: <empty>
ISA: Scanner SCSI adapter

Also have:

- 3 hard drives
- 1 zip drive
- 1 ls-120 drive
- 1 cdrom
- 1 cdrw

All working in blissful harmony in my full sized tower. I'm also a case modder, so I've got:

- 2 120mm fans
- 5 80mm fans
- 1 92mm fan
- 7 20mm fans

May seem like a storm is brewing, but if you know what you're doing, it can be clear as day.

Y'know, in a way, this is like the "640 KB should be enough for everybody" issue...

[jadison]

Heck, why even bother having PCI slots when they could just include sound, nic and video built into the mobo? ---> they do. :)

But, most of the time I prefer better cards, than what they have onboard!

-=jd=-

[Axel]

Why have so many PCI slots - because they can and there's a market -

It's been quite a while since I've had to fix an IRQ conflict. Years....

Most of the conflicts I've worked are either because the user has too many things fighting for the same system resources, or they have corrupt drivers. Then there's viruses and hard drives that have NEVER been defraged.....

Occasionally, I find a filled hard drive with over a thousand temp files that has never had it's temporary internet files deleted.....

As for combo boards - being a builder - which would you rather - on-board component conflicts you can never fix or upgrade - or the occasional IRQ issue that, while challenging, you can resolve given enough time and attention.

I won't own a combo board - you have almost no options and that board still uses the same IRQ's an expansion card would.... no gain - more frustration.... what's the point?

If your on-board component fries - most of the time you can toss the board. If a PCI card fries - you can replace it for less than $100 in most cases.... really easy choice there....

I hate to admit this, but looking at the total number of fans you have mootching juice off the power supply, did you ever consider that perhaps that very cool running system doesn't have enough watts to drive the peripheral devices? Never thought I'd say this in a life-time - but you truely have too many fans unless you drop in a second power supply.... Might not be an IRQ conflict - you may just not have enough power.

Next point - I've pretty much shunned zip drives all together because they caused me too many driver conflicts over the years.

With a burner in that system, once you have all your zip content burned to CD - remove that drive and ALL, and I do mean ALL, associated IOMEGA software and you should be in much better shape.

Next point - you have 5 different drive protocols there that I can see. The SCSI has it's own BIOS, and probably isn't an issue. but come on - decide - do you really need that multitude of drives on this box? Cut that down to two - probably EIDE/ATA and SCSI and ditch the firewire and zip - just eliminating those drivers, cards, and associated IRQ's will eliminate your problem. You need a network hub and about 3 machines - much more stable and flexible - what's your point here? That thing must dim the lights when you turn it on - not to mention it probably sounds like an aircraft carrier......

That's the best advice I can give you on this one -

I seriously doubt it's your motherboard - My original assertion was that you had too much junk in the one system - I'll stand by that based on what you've told us.....

A friend here suggests that you make an appearence on Tim Allen's Home Improvement with your PC -

Hey - been there - but I always end up removing a few components to resolve the issue - and that seems to lead me right into my next system build. Gotta put those components to use somewhere - right....

P.S. - your next motherboard - don't get an ISA slot - that'll leave you with one less head-ache at 5 MB/second speed. PCI is 132+ MB/second speed.....

[gmgq]

Again: My current system runs FINE.

Like I said, I am just talking about the whole IRQ issue in general. I'm talking about those occasionaly problems associated with IRQs from time to time which are not very obvious.

I wasn't saying that I condone combo mobo's. You were saying just have the necessities plugged into the PCI slots. So I was just saying if you want to do that, why not get a combo mobo and have 0 PCI cards. (I read your reply to this. I agree also, so this issue is settled).

I have an Enermax 450W PS. More than enough juice, I am fully aware of my system's power consumption.

I needed that zip drive for school, because that's the ONLY way I could transfer data back and forth. Their SGI cdroms couldn't read burned CDR/CDRW from home. Nor could we set up reliable web-based HD's to transfer the hundreds of megs of data we needed. Besides, my zip drive uses the default win2k drivers, no driver hassles at all. Plug & Play.

I need the firewire card to hook up my digital camcorder to it. I need to transfer 3D animations to the camcorder. Firewire is the only way to to achieve the speed required, so that I don't lose precious frame rates during the transfer.

The SCSI for the scanner is not a 'true' SCSI card. Like I said, it's a (cheap) SCSI 'adapter' that came with the scanner, to be used only for the the scanner.

I already have 3 other machines in the house, but I use my main system the most, so I like to have everything available here.

Again: My current system runs FINE. I'm just talking about IRQs in general. I did not start this thread pleading for help in resolving IRQ conflicts. I HAVE NONE.

[Hickman]

The only thing I don't like about my board is that the only isa slot on the board also shares the same irq as the usb ports. I have a sound card in that slot that I paid quite a bit for a few years ago, so I don't want to use the sound that is built into the motherboard. I have had a few problems getting the sound to work, but I turned the pnp os option off in the bios so that it will work.

It seems to me that the companies than manufacture boards could have taken these things into consideration when they designed it.