Help me with IRQ questions setting up my new Mobo

[chrisojeda]

Motherboard: MSI K7-Master (MS-6341)
Sound: Voyetta Turtle Beach Santa Cruz
NIC: Netgear FA311
Video: AGP (have not chosen yet, using a Voodoo 5 for now)

I would appreciate any help I can get setting up my new system. My motherboard has 5 PCI slots. As I am reading the book I have come accross the following which I don't understand:




"The PCI IRQ pins are typically connected to the PCI bus INTA#-INTD# pins as follows:

................Order1..Order2..Order3..Order4
AGP.............INT B...INT A...INT C...INT D
PCI Slot1.......INT A...INT B...INT C...INT D
PCI Slot2.......INT B...INT C...INT D...INT A
PCI Slot3.......INT C...INT D...INT A...INT B
PCI Slot4.......INT D...INT A...INT B...INT C
PCI Slot5.......INT A...INT B...INT C...INT D
SCSI 1..........INT C...INT D...INT A...INT B
SCSI 2..........INT D...INT A...INT B...INT C
AC97............INT C...INT D...INT A...INT B
USB.............INT D...INT A...INT B...INT C

AGP & PCI 2 shared
PCI 1 & PCI 5 shared
PCI 3 & SCSI 1 & AC97 shared
PCI 4 & SCSI 2 & USB shared
PCI 1~PCI 5:Bus Master"




1.)First, I don't really understand what exactly an IRQ is? I have gathered that it has to do with a channel of a sort that the hardware (pci card or other onboard hardware) uses to communicate. I can use further help to understand this concept.

2.)Next, I don't understand what the hell that chart is trying to say to me?

3.)I don't understnad how to use the information following the chart about the shared IRQs? I have heard people say that IRQ conflicts causes problems.

4.) I don't have a clue on which are the most strategic PCI slots to place my PCI cards and avoid conflicts (Turtle Beach Santa Cruz Sound Card & Net Gear FA311 NIC)?

5.) This BIOS according to the book allows me to manually assign IRQs. I am one who likes to learn and do things the best way possible to avoid pc issues. So if there is an option to do this I would like to do this. Though I need some help on knowing how to assign IRQs and I am sure this goes hand in hand with where to put the PCI card.

6.)What are the negatives of just letting the OS assign the IRQs (Windows 98)?

What can I say....I really need help in this area because I am a total newbie to this. If you have links to a website that explains all of this in detail that would be great also!...


It worked yesterday! :lol:

 

[Guest]

I'm sorry I don't have a link for you about IRQs but if you use a search engine(Google)you'll find the technical info you seek. You may let the OS or BIOS set the IRQs for your devices. Many installs procede without problems in this manner. If any of your devices are snotty about sharing an IRQ i.e. lockups,hangs,bsod it is possible to manually set a different IRQ for the device. This can be done in the BIOS of most new mobos. It can also be done in the OS in Device Manager. Some legacy devices also used jumpers. What mobo are we talking about here? It might be advantageous to post your complete system specifications as some guys can give you the exact recipe for your IRQ and PCI slot assignments.

 

[chrisojeda]

Hey man where is everyone?

It worked yesterday! :lol:

 

[jlanka]

Couple of things:

First, it would help greatly to know which OS you're planning on installing.

Second, IRQ's are simply an "address" so to speak that the Chipset/OS uses to reference the device it needs to access. An "Interrupt" is something that happens when there is data waiting to be read or written to or from a device. If the CPU is busily running through the instructions of your program, it will be "interrupted" which means that it has to put your program on hold while it runs whatever routine is necessary to service that interrupt.

That being said, AFA building your system you shouldn't worry TOO much about exactly where to place your expansion cards. What I usually do if I'm building a system from scratch is to start with just CPU, RAM and Video card. Then install the OS. Once the system is stable, start adding other expansions cards one at a time, make sure it looks stable after each one and then do the next one, etc. The most trouble you'll have is with your modem and/or sound card. BUT, W2K and 98/Me should be able to handle these smoothly 98% of the time.

Now, if your system appears to lock up or become flaky after inserting a card, then I would usually try it in a different PCI slot. That usually helps.

Also, as mentioned in this forum many times before, there is a thing called ACPI which basically means that the OS (especially W2K) will be able to reassign almost all expansion devices to one or 2 IRQ's (which looks scary to most) but don't worry - in most cases this is perfectly acceptable and will result in even easier installation. (NOTE I said MOST cases).

Lastly, if you get to a point where ACPI isn't working for you, you have the option on most boards of turning that off, and if you really need to the BIOS will allow you to assign specific IRQ's to specific slots. But this should only be necessary as a last resort.

IMHO, us usual. YMMV.

 

[dmcmahon]

I have found that IRQs and INTs do matter. INTs are low-level hardware interrupt lines. There appear to be 4 of these for your board (that's pretty typical), and they're called INT-A though D. These are then mapped, in software, to an address where some code that responds to the interrupt request will handle it, and those addresses are called IRQs. It is best to have critical devices like the video and sound cards on their own hardware interrupts, unshared with any other card. The software should then automatically map these to different IRQ numbers (Win 9x/ME will, Win2K has a problem and always maps all devices to the same IRQ anyway).
Based on the information you provided, it looks like your board is wired in "Order 1". From this, I would say the following:
1. With the AGP card in, leave slot 2 blank so that it can have INT-B all to itself.
2. Put the sound card in slot 1 so that it can have INT-A all to itself.
3. Put the LAN card in slot 3 so that it can have INT-C all to itself. This assumes that you are disabling or don't have the on-board sound and/or on-board SCSI.
4. Put any other card in slot 4, where it will share INT-D with the USB bus. It's best if this is a low-speed device, for example in my system I have a modem card in the equivalent position.
5. Leave slot 5 blank so that the sound card can have INT-A all to itself.

 

[chrisojeda]

jlanka,

I have not decided on an OS yet. I can either install ME or 98. I guess I'd like your advice on which is best for someone who is looking to use their pc for hard core gaming mainly?

My board does have bios support for assign the IRQs manually. I guess I always got the impression that hardcore enthusiasts preferred to do that always. Though maybe I was wrong in that. I guess now I am understanding that even the experts let the OS do it (if the OS does it right) and only resort to manual to fix it when the OS is not doing a good job.

Thanks for you help jlanka....Chris



It worked yesterday! :lol:

 

[chrisojeda]

dmcmaho,

I appreciate your time and information. I plan on following your direction on card placement.

My board does not have SCSI...I guess they just make a single book for both the SCSI and non-SCSI version.

Well, if this works out great for me then I'll post this up for others with an MSI K7-Master....Chris

It worked yesterday! :lol:

 

[dmcmahon]

For gaming, definitely go with one of the 9X OSes, either 98SE or ME. I have found that there is less game compatibility with Win2000, also Win2000 forces all your devices onto the same (software) IRQ. There is no need to set the IRQs manually in the BIOS, unless you don't like the result once you boot up. You do need to make sure you have enough spare software IRQs available for the OS to assign, however. I have found that IRQs 11, 10, and 5 are often available, and on my system they're assigned to the Video, Sound, and LAN cards. Sometimes, however, you will find that you will have to share one of these with the USB because the BIOS ran out. This is despite having been careful to separate the devices on the hardware interrupts. To get around this, you would need to free up an interrupt in the BIOS that's not being used. On my system I needed to do this so that the USB wouldn't share an IRQ with the other three devices. I went into the BIOS and disabled COM2, which frees up IRQ3. So now on my system USB and the modem card are using IRQ3. I believe that just freeing it up would be enough so that the BIOS would assign it automatically; since I'm paranoid and my BIOS supports it, I just went in and assigned all the IRQs manually anyway, just to be sure.