Sometimes, the cause of internal IBM PC cards not working is the result of conflicts with IRQ (Interrupt Request Line), I/O (Input/Output) Addresses, or DMA (Direct Memory Access) channels. Two (or more) cards may be trying to simultaneously use the same IRQ, I/O address, or DMA channels. The net result is that the cards interfere with each others' operation at the hardware level, typically making the cards uncontrollable by drivers and software. These hardware conflicts need to be corrected before drivers and software programs will work with the cards.

Most motherboards also have built-in components that use IRQ, I/O addresses, and even DMA channels. For example, IRQ 7 is used by the parallel port upon most motherboards. So, you must make sure that your card isn't set to some resource that is also being used by a component upon your motherboard.

One good sign that you may have an IRQ conflict with your sound/MIDI card is when MIDI playback works fine, but MIDI recording doesn't. Many cards do not use the IRQ for playback (ie, polled output) but most all do use the IRQ for recording (ie, interrupt-driven input).

Plug and Play (PnP)

The very first IBM PC cards that came out were designed to be plugged into ISA bus slots. Later, PCI and AGP bus slots were added to motherboards for newer PCI and AGP cards.

The ISA bus is much more primitive than PCI and AGP, and therefore the configuration of ISA cards is less automatic and more troublesome. Typically, you have to manually set "jumpers" or DIP switches on an ISA card to determine the IRQ, I/O address, and DMA channels that you wish the card to use.

On the other hand, most all PCI and AGP cards have a feature called Plug and Play (ie, PnP) that lets the computer itself configure the cards to resolve all hardware conflicts. So you don't have to manually set any jumpers or DIP switches for PnP cards, nor inevitably worry about hardware conflicts... at least in theory. This assumes that the card wasn't cheaply made to support only a limited set of the possible IRQ numbers. (ie, Some manufacturers will make PnP sound cards which only allow a choice of the most common IRQs used by sound cards; 5, 7, or 9. They do this to save a few pennies. But this can be really bad if you happen to have a few other cards that only support these same few IRQs such that there aren't enough IRQs to dole out among the cards). Furthermore, some older motherboard BIOSes have bugs in their PnP code such that conflicts aren't properly resolved. (In this case, either update your BIOS, or if using an OS that supports PnP, such as Win95/98/2000, see if you can disable your BIOS handling of PnP and let the OS setup the cards' IRQs and base addresses). So, it's still possible (but rare) to see hardware conflicts with PnP cards.

Some companies have tried to make ISA cards that allege to be PnP, but ISA cards don't really support PnP. An ISA card that alleges to be PnP may or may not work properly with real PCI PnP cards. In my experience, they don't, and should be treated as non-PnP cards.

Hardware conflicts are very common if your sound/MIDI card is not PnP (or if you have other types of cards in your computer which are not PnP). Non-PnP cards may interfere with the operation of PnP cards (or vice versa) if you don't properly setup your computer's BIOS and Windows' Device Manager. So, unless your computer system has all PCI (and AGP) cards in it and does not have any ISA cards, then you should definitely check for hardware conflicts.

Checking for conflicts

For non-PnP cards, do physically inspect the cards to make sure that every one is set to a different IRQ and base address. I can't possibly stress this enough. If you're not sure what IRQ's the non-PnP cards in your system are using, then open up the case and take inventory. (I urge anyone who buys a pre-built system to insist, when you buy the system, that the vendor provide you with a list of any non-PnP devices in the system indicating which IRQs, base addresses, and DMA channels are used by those devices. Demand it. And then make sure you do get it). Apparently, there are lots of people who enjoy playing what I call "the IRQ guessing game". Without knowing what IRQs, base addresses, and DMA channels are in use in his system, this person will arbitrarily set the jumpers on a non-PnP card being added to his system, install the card, and then hope that when he boots up everything will magically work. It usually doesn't. In fact, by the time that the person has played this game for a suitably long time, monkeying around with drivers, he has really messed up his entire software installation. It isn't worth doing that when, if you have a list of what devices use which resources in your computer, changing or adding hardware to a PC is typically a very simple, quick, trouble-free process. I've done this a lot to my own system and others' systems. (You know all those horror stories about installing PC cards? They come from people playing the "IRQ guessing game").

If you have non-PnP cards, don't rely upon Win95 (or any other OS) telling you if you have an IRQ or base address conflict. The ISA bus does not support determining this, so OS's (and utilities such as MSD.EXE) have to perform a sort of "guessing game" of their own, assuming certain "standard and/or typical" IRQ settings, and then checking for anything that looks like a deviation from this.

In order to unequivocally determine what IRQs, base addresses, and DMA channels are in use on non-PnP devices, you need to know the jumper/DIP settings of your cards. This includes all of your ISA cards as well as any non-PnP devices on your motherboard. IRQ conflicts appear to be the biggest cause of conflicts. Base address and DMA conflicts aren't nearly as common (but if you have 2 or more of the same type of card in your system, for example, 2 MIDI/audio cards, the chances of base and DMA conflicts increase dramatically as many manufacturers of the same types of cards follow each others' "standards" for IRQ/address/DMA settings. For example, most MIDI cards use the Roland MPU-401 standard I/O address of 330). Here's a list of what I've found to be the most common IRQ assignments. I think that it's pretty safe to assume these, but beyond the standard devices (ie, clocks, keyboard, serial + parallel ports, HD and floppy controllers, math chip), check all of your other devices:

0      System timer
1      Keyboard
2      Cascade for second interrupt chip
3      Serial (COM) port 2 (often a modem is attached to this)
4      Serial (COM) port 1 (usually a serial mouse is attached to this)
5      Parallel port 2 (not often used)
6      Floppy controller
7      Parallel port 1 (usually a printer is attached to this)
8      Realtime clock
9      free (but some video cards may use this for EGA emulation)
10     free
11     free
12     free
13     Math chip
14     HD (IDE) controller
15     Second IDE controller (usually a CD-ROM is attached to this. This second
       IDE controller may even be on your sound card, such as an SB card)

Typically, sound cards are set to use IRQ 5. This is often a good choice. Usually, IRQs 10, 11, and 12 are safe to use (assuming other ISA cards aren't using such). If the card has a MPU-401 compatible MIDI port, it usually uses I/O addresses 330 and 331 (hex). The MIDI port may also use another IRQ such as 9, separate from the IRQ used by the digital audio portion of the card.

Checking for conflicts using Win95/98/2000 Device Manager

Win95/98/2000 are PnP aware operating systems. This means that they can not only determine (and display for you) what IRQs, I/O addresses, and DMA channels are in use by all of your PnP cards, Win95/98/2000 can also let you change what IRQs, I/O addresses, and DMA channels are used by each PnP card. You may be able to easily resolve any conflicts just by using the Win95/98/2000 utility that controls IRQ, I/O Address, and DMA channel assignments. That utility is the Device Manager page of Control Panel's System utility.

Here's what you do to get a listing of what IRQ's are being used for what on your system. Go into Control Panel, run the System utility, and turn to the Device Manager page. Click on the Print button. Ask for a "System Summary". You'll get a listing (actually a .prn file that you must print out) that has a section which on my system looks like this:

       ******************** IRQ SUMMARY ********************

       IRQ Usage Summary:
         00 - System timer
         01 - Standard 101/102-Key or Microsoft Natural Keyboard
         02 - Programmable interrupt controller
         03 - Sportster 28800 Internal
         04 - Communications Port (COM1)
         05 - Printer Port (LPT1)
         06 - Standard Floppy Disk Controller
         08 - System CMOS/real time clock
         11 - Adaptec AHA-2940U/AHA-2940UW PCI SCSI Controller
         13 - Numeric data processor
         15 - Diamond Stealth 64 Series (Diamond GT)
This shows me what devices are using which IRQs. For example, IRQ 11 is being used by my Adaptec SCSI card. My Diamond video card is using IRQ 15. You'll notice that IRQ 12 isn't shown in this above list. That's because no device is using that. So if I were to add a new non-PnP card to my system, I'd set it to use IRQ 12 for example. (If you have some device that is using an old Win3.1 driver rather than a newer Win95-aware driver, it may not show up in the above listing. For example, my RAP-10 Sound Card has an old Win3.1 driver. It doesn't show up in the above list even though I have set it to use IRQ 7. So although IRQ 7 is not shown as being used in the above list, it really is. That's why it's so important to have all Win95-aware drivers on your system. Otherwise, Win95 may not be able to properly setup PnP peripherals because it may not know that some device is using an IRQ. Always update all drivers and avoid using Win3.1 drivers on your Win95 system, especially if you have PnP cards. If you must use a non-PnP card with a Win3.1 driver, then at a minimum, go into your BIOS' PnP configuration screen, and set the IRQ used by that card to be reserved for a "legacy ISA device").

If you've got a conflict, you'll typically see two cards listed using the same IRQ. For example, here's a conflict between my printer and sound card:

       ******************** IRQ SUMMARY ********************

       IRQ Usage Summary:
         05 - Printer Port (LPT1)
         05 - Jeff's Sound Card
You may also want to check the IO Port Summary to make sure that no 2 cards have address ranges that encompass the same values.

Incidentally, that small yellow exclamation mark (or red X) you see next to a device name in "Device Manager" indicates a conflict (usually IRQ) or that something is wrong with the device's response. (ie, For example, I use SCSI devices rather than IDE, so I disabled my IDE ports. My PnP BIOS told Win95 that I had IDE ports, but Win95 didn't get any response from them, hence that exclamation mark next to my "PCI IDE controller". In fact, it's common to see exclamation marks related to PnP ISA cards. Often the devices appear to have several "phantom" units, each one dedicated to whatever IRQs the device supports, and Win95 thinks that these are real yet gets no response from them. Hence you may see several instances of a particular PnP ISA card listed, with all but one having an exclamation mark. It's OK to leave these phantom devices, and if Win95 ever tells you it detected new hardware the next time you boot, tell Win95 to ignore each one of those phantom devices as it pops up a dialog for each, asking you to choose a driver to install. Better yet, select the Properties of each one of these Phantom devices, and remove the checkmark next to "Original Configuration". This helps free up that wasted IRQ for another PnP card which will really use it, rather than simply reserve it for no good reason).

NOTE: If you have Windows 98/2000, a new feature was added to Device Manager which pretty much displays all of the info that you saved in that .prn file produced by Device Manager's Print feature. Just double-click on the "Computer" icon in Device Manager. This will bring up a dialog box that can show lists of which devices are using which IRQ numbers, I/O addresses, and DMA channels.

Solving conflicts

The way to solve hardware conflicts depends upon whether the cards in conflict are all Plug and Play (PnP), or whether one or more of them is a non-PnP card.

If the two, conflicting cards are PnP, then you're in luck. All of the hardware conflicts can be resolved just by using Windows' Device Manager. You won't even have to open your computer case. (But you should make sure that you have the latest version drivers for those cards. Sometimes, updated drivers solve what appear to be hardware problems with PnP cards). Merely go through Device Manager's IRQ, I/O Address, and DMA channels lists to note any resource conflicts, and then use Device Manager to change the Properties of any conflicting cards and set them to use unique IRQ, I/O Address, and DMA channels. For PnP cards, you can change a device's IRQ or I/O Address Range by clicking on the device's name in the Device Manager list, clicking the Properties button, and turning to the Resources page. Uncheck the "Use automatic settings" box. Now you can click on any individual "Interrupt Request" or "Input/Output Range" setting to change its IRQ or I/O Address respectively. Click on the "Change Setting" button to pick a new value for that setting.

If one of the conflicting cards is PnP, and the other is non-PnP, then you may be able to resolve the conflict by adjusting your computer's BIOS PnP configuration. You should reserve any IRQs used by non-PnP cards -- setting each of those IRQs to be reserved by a "legacy ISA device". At worst, you'll have to open the computer case and change jumpers or DIP switches on the non-PnP card.

If both cards are non-PnP, then you'll have to open the computer case and change jumpers or DIP switches on one of the cards.

In conclusion, here is a list of things to do to solve hardware conflicts:

  1. If you have non-PnP cards in your computer, first make sure that you know what IRQ, I/O Addresses, and DMA channels (if any) that these cards are using. Don't depend upon Windows to be able to tell you. If you don't know, physically inspect the card's jumpers or DIP switches. Write this information down.
  2. If you have PnP cards in your computer, make sure that your motherboard's BIOS is a PnP-aware BIOS, and make sure that it's the latest version of that BIOS. Check the web site of the motherboard manufacturer for any BIOS update for your motherboard. They may have an updated BIOS to download, plus a utility that installs it, and instructions how to install it.
  3. If you have non-PnP cards in your computer, go into the BIOS setup screen. (This is usually done by pressing the Delete key while the computer is just starting to boot). Go to the PnP configuration page. Choose a manual setup (rather than an automatic one). For every IRQ that is being used by one of those non-PnP cards, set that IRQ to be reserved for a "legacy ISA device" (rather than used for "legacy ISA/PCI"). Note that your mouse may not work in selecting items in the BIOS setup, so you typically have to use the arrow keys to move between selections, and the Page UP and Page DOWN keys to change the value of a selection.
  4. Use a PnP-aware operating system such as Windows 95/98/2000. Use Device Manager to check for any hardware conflicts, and if any of the conflicting cards are PnP, use Device Manager to change the resources so that conflicts are resolved.
  5. Make sure that you have the latest versions of all drivers for your cards. Check the web site of each card's manufacturer for any driver update for that card. They may have an updated driver to download, plus instructions how to install it.

Driver issues

Another, even more common problem concerns software drivers. The fact of the matter is that programmers do write buggy software, and there's a chance that any problem which looks hardware-related may actually be due to some bug in the card's driver. Check with the card's manufacturer that you have the latest drivers. Ask if there have been any problems reported that may be applicable to your own setup.

And definitely don't rule out the possibility that you may have configured the driver's setup (ie, "Properties" in Microsoft-speak) incorrectly. If you use Windows 95/98/2000, read the FAQ "MIDI/Audio under Win95/98/2000".