Smart questions
Smart answers
Smart people
Join Tek-Tips Forums

Member Login

Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you a
Computer / IT professional?
Join Tek-Tips now!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Tek-Tips
*Tek-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

KlondikeMike (TechnicalUser) (OP)
27 Jun 01 7:41
Howdy all,
First off, my system:
Win2k Pro (SP 2), Intel OR840G mobo (latest BIOS) with dual P-III 933's, 512-MB PC800 RDRAM, a 3dLabs Oxygen GVX1 graphics card, NetLine 10/100 PCI NIC, Sound Blaster Live!, Adaptec 2930cu PCI SCSI w/HP 9200i CD-RW, Panasonic DVD/CD-ROM, 2 Western Digital EIDE HD's running thru the integrated ATA66 controller on the mobo.
All drivers are the latest versions.
Page file size is set to 766-MB (min) 2000-MB (max) and is located on C:.
System resouces never drop below 76% from a start of 85% (according to AnalogX's MaxMem).
Also using IE 5.5 (SP1) and Zone Alarm.
My problem:
I've got a slight stability issue with one of my programs.
It's a 3D modeling/animation application. Lots of users of this program have crashes, while others can use the heck out of it for months without failures.
Sometimes it will totally freeze the system, while other times it will cause a reboot. It never happens while I'm doing the same operation (ie: very random)
Some user-reported crashes are caused by user error (ie: doing something that the program doesn't like), and other crashes are truly hardware related.
I have recently checked Device Manager to see if there were any hardware conficts and none were indicated, but I noticed that my graphics card and my NIC are sharing IRQ 16.
I know that in itself isn't a big deal, but since this program demands a lot from the hardware (especially the graphics card), I'm wondering if this could be the root cause of my crashes and, if it is, how do I go about reassigning the IRQ's?
My current IRQ assignments are:
1- keyboard
2- not listed
3- not listed
4- com1,
5- Intel 82801AA SMBus Controller
6- Floppy disk controller
7- not listed
8- System CMOS/Realtime Clock
9- Microsoft ACPI-Compliant System
10- not listed
11- not listed
12- Mouse
13- Numeric data processor
14- Primary IDE Channel
15- Secondary IDE Channel
16- 3dLabs Gamma Processor for Oxygen GVX1
16- 3dLabs Oxygen GVX1
16- NetLine 10/100 PCI Card
17- Creative SB Live! series(WDM)
18- Adaptec AHA-2930CU PCI SCSI
19- Intel 82891AA USB Universal Host Controller
There aren't any jumpers on the cards or mobo, and I don't think the Intel mobo let's you assign IRQ's with the BIOS.
This program is the only one that crashes on my system. I also use Photshop 5.5 and Painter 5 to create/manipulate large graphics files (90+ megabyte images, with unlimited Undo's) up to 8-12 hours a day without any problems ever. But they are 2D apps, and not nearly as stressful to the graphics card as the 3D one is.
I'm not adverse to changing to a different brand graphics card or NIC (a LOT cheaper than a new grahics card) if it will do me any good. Any ideas?
Michael Comeaux
KlondikeMike (TechnicalUser) (OP)
27 Jun 01 7:48
Howdy again,
Just remembered to add to the previous post:
The fans on the graphics card are operating normally, as well as system fans and case fans and the exhaust air coming out of the PSU is about 5+ degrees cooler than room temperature.

Michael Comeaux
Helpful Member!(2)  CitrixEngineer (TechnicalUser)
27 Jun 01 8:23
Maybe someone will correct me on this, but aren't PCs limited to 16 hardware interrupts, from 0 - 15?

If there's a graphics card interrupt issue, most BIOSes will allow you to manually assign an IRQ to the graphics card. I don't know the BIOS on your particular mobo, though.

All the other cards should be handled through PCI Interrupt sharing, which is usually handled fairly well through the O/S and appropriate manufacturer drivers.

Have a look at my faq on Virtual memory for a few ideas on this which may help.

Try improving the cooling inside the case - it could be a heat issue - or heat could well be a factor.

Hope these suggestions help
Zorlod (MIS)
27 Jun 01 8:30
Go into your device manager and see if you can change the irq of your NIC to interupt 10, this is fairly standard for most NIC's anyways.  You may have to reserve an interupt, remove the nic and reinstall it.  If not, maybe try and see if another NIC will default to irq 10 or let you switch it there.
Helpful Member!  butchrecon (MIS)
27 Jun 01 8:48
CitrixEngineer is correct. PCs are limited to 0-15. If yours is stating 16-19 then your OS is haveing problems ie... Corruption or virus. Though I do admit that I am not familiar with dual processor boards.

Please let us (Tek-tips members) know if the solutions we provide are helpful to you. Not only do they help you but they may help others.

James Collins
Computer Hardware Engineer


KlondikeMike (TechnicalUser) (OP)
14 Jul 01 3:48
Howdy guys,
Here's an update to my IRQ-sharing NIC & graphics card dilema:
The Realtek card isn't configurable, so I'm stuck with whatever IRQ it grabs. The mobo BIOS doesn't allow IRQ assignemnts from users, nor can I reserve IRQ's from within Win2K Pro (at least, I haven't found that option to be available).
Removing the NIC's references from device manager and then
changing the PCI slot before booting didn't change anything, nor did removing the graphics card refences from the device manager and rebooting help.
Since I've been wanting to get all non-grahics apps out of my Win2k environment anyways (my wife uses Office 2000 Pro which I've heard is a memory-leaking resource hog)), I wiped everthing out and made it a dual-boot setup with Win98 for her stuff and Win2k Pro for my graphics apps.
Now my 3-D app is MUCH more stable and I can use it for many, many  hours without crashes. It still does it once in a while, but not anywhere near as often as before.
The IRQ-16 is still shared by the NIC and graphics card (though not in Win98), so I know this wasn't a true solution to the root problem.
I'm going to be doing some hardware upgrades soon and will look into getting an NIC that allows IRQ selection or at least uses something other than IRQ-16.
And, later this year or early next year, I'll be switching from a dual-Intel setup (the Intel mobo's don't allow much in the way of user-configurability) and will go with a dual-Athlon system with a non-Intel mobo (I'm waiting for other dual-Athlon mobo's to hit the market, as I've been smited down in the past with the problems of early adoption of new hardware. Once bitten, twice shy, my friend. Also, the longer I wait, the more brands to choose from, the better the prices).
And if all that doesn't change things, I'll be buying a different brand graphics card. The nub of it all is that I recently moved to Oregon from Alaska and don't have any techie friends yet to swap out hardware with to chase down such conflicts.
But this list is proving to be the next best thing to it.
Thank you all for your helpful suggestions! I'll make sure to post an update when I change mobo's later on.
Michael Comeaux
butchrecon (MIS)
14 Jul 01 7:56
I am still confused on the IRQ-16 thing. Never have I seen that. Even on dual boot systems.

James Collins
Computer Hardware Engineer


Please let us (Tek-tips members) know if the solutions we provide are helpful to you. Not only do they help you but they may help others.

KlondikeMike (TechnicalUser) (OP)
21 Jul 01 7:36
Howdy butchrecon,
There's a short article about IRQ sharing with Win2k located at:
Apparently, Unca Bill has decided that we no longer can be trusted with choosing our own IRQ, or he/Microsoft was unable to force the hardware manufacturers to exclusively use "x" IRQ for modems, "y" IRQ for video, "z" IRQ for sound, etc.., or (better yet) radically increase the number of actual IRQ's.
The graphics IRQ and NIC IRQ aren't shared using Win98 due to the fact that it doesn't implement ACPI, while Win2k does (unless disabled before, or after installation of the OS). But, since I'm using SMP, I'm stuck with ACPI and the shared IRQ's.
I'm thinking of disabling the NIC while booted into Win2k to see if I can get bullet-proof 3-D modeling. Kind of a hassle not to have internet access without rebooting to Win98, but I might try it for a while and see what happens.
Anyways, hope the Microsoft article sheds some light on the subject for you.
Michael Comeaux
butchrecon (MIS)
21 Jul 01 10:57

I understand the whole IRQ sharing situation under Win2K quite well. What I am having problems with is the IRQ 16 thing. Its not that I dont believe them, I just have not seen an IRQ 16 in my entire career. But thanks for the article. It may help others.

James Collins
Systems Support Engineer


Please let us (Tek-tips members) know if the solutions we provide are helpful to you. Not only do they help you but they may help others.

KlondikeMike (TechnicalUser) (OP)
21 Jul 01 17:58
Hi butchrecon,
Didn't mean to come off condescending. After I posted this morning I found a different thread in the Win2k section where it was obvious that you have knowledge of PCI IRQ steering.
Before using a dual-processor system under Win2K Pro, I had never seen IRQ-16 or above either, and I have been fixing computer problems since 1982 (sophmore in highschool) when I started transitioning from traditional art to digital art. Computers were less than powerful so, as technology improvements started increasing more rapidly, I did my best to stay on top of any upgrade that would allow me to create stuff with more of a real-time feel. Upgrading was a rocky road back then, and I spent almost all of my spendable income on new hardware & software. The constant, aggressive upgrading (as well as my obsession to tweak things) meant diving in to solve hardware conflicts on a regular basis just to get new things to run. The hardware was expensive as heck, which meant no money to pay someone else to install things and troubleshoot it. Anyways, the long & the short of it is: I've spent enough on computers to have put a down payment on a house, I made a lot of mistakes, learned a lot about diagnosing problems, and now have my own business working on other peoples computers. I'm a 2nd generation computer technician (my dad recently retired after over 40 years in the field), I don't know everything (which is why I'm a member of this forum), and have no certifications yet, but I've never failed to get someones computer back on the road.
I don't know why Win2K says there's anything above IRQ-15 either. But it does, and I'll keep scouring the internet until I find out why (maybe they thought it would warp our fragile little minds if we knew that multiple devices are actually sharing IRQ-9, instead of being assigned "real" IRQ's). Shakespeare was wrong about there being nothing new under the sun...
butchrecon (MIS)
21 Jul 01 19:59
I have been through both the MS MSDN and TechNet areas of MS and found nothing on IRQ 16. I did not take your comment as condescending. I thought you were a bit confused on what I was asking. No big deal. I have not been working on them as long as you, but I am newbie either. I ran a computer shop for three years, and like you I have spent enough on upgrading my machine to purchase a new machine every year for life.
I have never run across the IRQ16 thing (Though I admit FREELY I do not know everything.) I am hoping there are others out there who ran into IRQ16 like you. I am interested in finding out more on it. So far nothing.

Not related to this forum (what I am about to type), but something you said is correct.
You are also correct on not knowing everything is a reason for the forums. I ran into a lot of people in the retail world (Its WORSE in the corporate world) who read 1 book and think they are experts. I would have customers constantly come in and try to make themselves look smart. (never worked). Now that I have migrated to the Corporate IT world it seems worse. Since being hired into my current position 2 years ago I have found that many here were I work know nothing. Some with certifications out the wazoo who spent 6 weeks earning them. So far I have found many on this forum who genuinely know what they are doing. And I like that.
Anyway I am rambling.

James Collins
Systems Support Engineer


Please let us (Tek-tips members) know if the solutions we provide are helpful to you. Not only do they help you but they may help others.

Guest (visitor)
29 Jul 01 17:43
I am also having a bit of trouble with IRQs 16+ for some strange reason (and i know that my motherboard states i should only have irqs 0-15) W2k has assigned irq 16 to my inndo tornado invidia 64mb geforce2 mx 400 card and to my soundblaster xgamer card, then my modem gets irq 17 and i suppose on down the pci chain...this is really really wierd and its causing an IRQL_NOT_LESS_OR_EQUAL error when i am trying to play diablo II online.  And on top of that i cannot go into the hardware manager and change the settings for the memory ranges or irqs. it is bad and its a fresh install of w2k on a tyan tiger 133 motherboard with 2 pIII 800eb coppermine processors. the modem is a modem blaster flash 56 from creative.  i really need help
KlondikeMike (TechnicalUser) (OP)
29 Jul 01 21:30
Hello Grogramin,
You're stuck with IRQ saring as long as you're running Win2K set up for dual CPU's.
For the record, I got my alphabet soup jumbled in my last post: it not "ACPI" (power management), it's "APIC" (Advanced Programable Interupt Controller). Two birds with different feathers.
If you're using the dual-CPU's for apllications that support multi-threading, but also want to play your games reliably, the only recourse I can see is to make your system dual-boot between Win9x and Win2K where your games are played through Win9x and your multi-threaded apps are run through Win2k.
Most games don't utilize two processors anyways. Quake 3 is the only one I'm aware of, but I'm not a hardcore gamer anymore, so there could be others.
As a side note, reserving IRQ's at the BIOS level won't do anything for you, as APIC disregards that info when Win2K boots.
I've been searching for info on APIC to see if it absolutely neceassry for using dual-CPU's with Win2k, and haven't found anything on it yet. Without APIC enabled (i.e.: not installed at the time of OS installation, or uninstalled after OS installation) you should be able to manually configure IRQ's in Device Manager. But a dual-CPU environment is a tricky beast, and might require the use of APIC.
Hope some of this helps you.
Michael Comeaux
mcvpjd3 (IS/IT--Management)
30 Jul 01 6:14
OK, I don't know about the IRQ 16 issue, but if you want to change your IRQ's, then here's a report of my post on how to change your IRQ's in Win2K

OK. This is not easy. I've had to do this because Microsoft think they know more about computers than anyone else and therefore decided not to let us play with our IRQ's ourselves. What you want to do is possible, but if you follow my advice, it's at your own risk, this can go very badly wrong!!!

The problem is ACPI, ACPI controlls the sharing of your IRQs and will not let you change them, what you need to do is convince Win2K that your PC is NOT an ACPI compliant PC. To do this do the following;

(Detailed steps in case others need to do this)


Click on Hardware, then Device Mangler

Click the + beside Computer and under that should be Advanced Configuration......(ACPI) PC

Double Click on this;
Click on DRIVER Tab;
Click on Update Driver;
Click Next;
Check - Show All hardware....;
Select STANDARD PC, next, and when finished Reboot PC.

WARNING!!! - This will lose your hardware and when rebooted it will re-detect all your hardware, make sure you have all your drivers ready (I suggest copying them to the Hard Disk First!!!)

When you have rebooted (as many times as needed to get all hardware back) then you need to stop IRQ steering, this is done by;


Click on Hardware, then Device Mangler

Click the + beside Computer and under that should be STANDARD PC

Double Click on this, select the IRQ Steering Tab,
and you can either disable IRQ or (what I used) was Get IRQ table from Real Mode PCIBIOS 2.1 Call (get's IRQ based on BIOS and what slot the PCI card is in).

This may or may not let you change the IRQ's (depends on MoBo I think), but it will not put eveything on IRQ9 (or IRQ11 Sometimes), and will change IRQ's if you change the card order in your PCI slots.

So far my machine has been very happy about this (with all 5 PCI devices, AGP, USB, etc...) but it no longer shuts down automatically.

Hope this helps.

Any questions let me know.

Oh... and.... good luck - remember my warnings.



Guest (visitor)
6 Aug 01 16:46
yea yea  laugh at the name all you want the fact is im poor and have a p2 400 mHZ comp with an intel mother board with a front side bus speed of 133 mhz. My problem is also dealing with the very difficult IRQ. Well I just bought a nvidia geforce2 mx 400 with 64 megs of RAM. I bought this for myt high speed gaming such as Team Fortress Classic, thats the good news :D. Unfortunately my IRQs want to be a pain and assign hard ware to different places such as my new video card which is in slot 10 when its supposed to be in 11:(. My question is how would i rearange my hard ware to different slots through BIOS. my version of BIOS is 1.14. Please help.
Guest (visitor)
3 Sep 01 12:27
This is in reply to Patrick (mcvpjd3):

I got a very similar problem under Win2000, with a Dual-PIII Dell 420 Precision Workstation and using a National Instrument A/D board. Such a card always got IRQs higher than 15, depending on the slot and independently on the BIOS settings.

By the reported procedure, it is possible to let the user assign IRQ and I could perfectly solve my problem.
However the "Standard PC" installation is not anymore supporting the Dual-Processor. Isn't it too bad? Is there any other chance to decently a Dual-Processor without such a IRQ automatic assignment?

tsessoms51 (IS/IT--Management)
28 May 02 1:07
I'm having the same problem with 2 servers. Both are dual Athlon, 1 mobo is a Tyan Tiger, the other is a MSI K7 Master. Both have Adaptec U160 Raid(irq10)and 2940 (irq11) SCSI controllers and Dlink 570TX 4 port NIC (irq5). After Win2k finishes doin it's magic, on BOTH servers: The U160 and nic port 1 are on irq16, the 2940 and port 2 of the nic are on irq 17, nic port 3 is on irq 18, nic port 4 is on irq 19. Load balancing is also enabled on the NIC. The problem does not occur with load balancing disabled.

The problem is that when a user downloads a file >2.5mb from the server (via file manager or html) the server blue screens with STOP x...1 IRQL_NOT_LESS_OR_EQUAL error. The IRQL eror is in technet. My own opinion (based on 25+ years experience) is that we have a basic irq conflict.

If I open the registry to HKLM \ Hardware \ Devicemap \SCSI I can see and change the remapped irq's for the SCSI adapters. What I cannot find in the hive is the remapped irq's for the NIC.

I've been able to get the AHA2940's back on irq 11. Now I want to move nic port 1 to irq 20.

What I have not been able to locate is info on how many high irq's are useable. Anyone know???
CitrixEngineer (TechnicalUser)
28 May 02 3:52
OK, I did a little research on this;

IRQLs are a different thing to IRQs.  A PC still has 16 IRQs, because that is part of the limitations of design of the i8259 PIC (Programmable Interrupt Controller). If a machine is built using Advanced PIC (i8259A), then it can route up to 256 interrupt lines.

Windows 2000 maps virtual IRQs, or IRQLevels via the HAL. This gives Windows 2000 greater control, which is why it is generally more stable than 9.x, except when it comes to handling exceptions (as tsessoms51 posting). This means that an IRQL is NOT the same as an IRQ, and should not be treated as such. An IRQL is controlled by the HAL until it can get an actual IRQ from the PIC.

There is no way for you to know what actual level Windows 2000 is using, since it's all virtual. You can view the assignments in a debugger using !idt (Interrupt Dispatch Table). The IDT is where Windows 2000 maps the hardware IRQs and configures trap handlers for exceptions.

(Hope this isn't too much information - I always enjoy research projects!)

I would guess, therefore, that this is more driver-related than IRQ related. Which service packs are being run, and are you using the latest drivers for all your hardware?

dinosnake (IS/IT--Management)
30 May 02 21:53
Thank you, CitrixEngineer - I figured that was it.  IRQ's are actual electrical lines connected to the controller - you can't add IRQ's without adding another controller - and thereby break the IBM architecture.  Upon reading this thread I realized that it must be logical - and so it is!

What a lousy idea!! Yet another VxD abstraction layer in the driver stack - this time for hardware handling itself!!  It also means that the OS is even doing more, as it must route the requests (as I am sure that this is not supported in the APIC hardware).  Latency, anyone??
Antimatter (IS/IT--Management)
30 May 02 23:51
I've seen a few instances of non ACPI compliant modems and NICs causing errors when sharing interrupts with other devices under Windows 98 and 2000.
My suggestion would be to try a different NIC or updated driver.
In desktop systems that I'm more familiar with, PCI slot 1 often is designed to share an interrupt with the AGP so it's best to leave that slot free.  I'm not sure how Intel workstation boards are designed in that respect.
Speccie (TechnicalUser)
3 Jun 02 5:50
Well James, I have to put my fourpence in. I have worked in ISA and microchannel architecture and IRQ 15 is max to my current knowledge. It is electrical lines on the bus, but not 16 (0-15) it is 4. The IRQ's are counted in binary so its 1/2 a byte. An IRQ is an interrupt in old currency and devices that can share, ship an address along with the interrupt, devices that dont ship an address can't share....Its as I know it. I also know that in Win9x IRQ's can be altered for devices that share, for instance I have  busmasters on IRQ 14 and IRQ 15 and if I open device manager and select hard disk controller and properties, click on resources, I have a choice of selecting another configuration. I am using a thinkpad 770 and I have so many shared devices I have to close ones I dont use. Attaching the machine to a docking station adds a 3rd busmaster. This has to be shared with IRQ 15. In win9x, start, run, type in msconfig and IRQ's and other resources can be investigated. Below a copy of my current active IRQ's.

0    System timer
1    Standard 101/102-Key or Microsoft Natural Keyboard
2    Programmable interrupt controller
3    (free)
4    Communications Port (COM1)
5    Crystal PnP Audio System CODEC
6    Standard Floppy Disk Controller
7    Printer Port (LPT1)
8    System CMOS/real time clock
9    Crystal PnP Audio System MPU-401 Compatible
10    D-Link DWL-650 11Mbps WLAN Adapter
11    IBM CD1M MPEG-2 Decoder Card
11    IBM ThinkPad 770/770E/770ED (Cyber9397)
11    Texas Instruments PCI-1250 CardBus Controller
11    Texas Instruments PCI-1250 CardBus Controller
11    Intel 82371AB/EB PCI to USB Universal Host Controller
11    IRQ Holder for PCI Steering
11    IRQ Holder for PCI Steering
11    IRQ Holder for PCI Steering
12    IBM PS/2 TrackPoint
13    Numeric data processor
14    Standard Bus Mastering IDE Hard Disk Controller
15    Standard Bus Mastering IDE Hard Disk Controller

The above is a copy and paste from msconfig, if I got this wrong, I need re-educating, I also did a search with no hits.

regards Michael.
MA5 (TechnicalUser)
3 Jun 02 10:21
Hi all
What an interesting thread so let me confuse the issue a little bit and that might through a light on IRQ16 (if it exists).
On the original IBM PC architecture, the IRQ coordination was handled by a chip capable of up to 8 interrupt lines (in case of IBM, it was Intel 8259 controller chip).
As demand for IRQs excided the numbers available. IBM added another Controller chip in their IBM PC/AT design. To maintain compatibility levels, they piggybacked the new chip to the original and hard wired the new IRQ9 to the original IRQ2, so all the IRQ 8~15 requests were and still are handled by IRQ2 (that is why it is an interrupt request controller) and hence higher priority of IRQ8 to 15 over 3 to 7.

Now, is it possible that a manufacturer has added a third controller chip! In effect creating IRQ 16 to 23!
If so BIOS and the OS used must be IRQ 16 to 23 aware.

CitrixEngineer (TechnicalUser)
5 Jun 02 3:26
I haven't read all of this yet - there's far too much of it - but it covers this in incredible detail, including interrupt vector mapping, chaining of controllers and how interrupts are assigned. It also distinguishes hardware interrupts from software INTs, and discusses how latency is handled. can also brush up on your assembly programming while you're there...

There's another good document here (which is a bit easier to read!);

This is more from the angle of the processor support (for up to 255 interrupts). Be careful to distinguish between x86 and 8259 processors!

Finally, here's a presentation style document that covers how IRQs are handled by Windows 2000 (it looks like it might be a research paper);


Reply To This Thread

Posting in the Tek-Tips forums is a member-only feature.

Click Here to join Tek-Tips and talk with other members!

Back To Forum

Close Box

Join Tek-Tips® Today!

Join your peers on the Internet's largest technical computer professional community.
It's easy to join and it's free.

Here's Why Members Love Tek-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close