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View Full Version : Re Arrange my IRQ's



aagiants
11-12-03, 07:13 PM
Is there a way to do this?
Irq 2,3,4,6 are not even used
11-15 are used like 4 times each..
all other are used once...
i have maxed out my PCI slots and wish to do this to give more resources to each device...

Sid
11-12-03, 07:34 PM
There's lots of threads here about forcing IRQ's. You will get views from both sides. YOSC say's he perfers it, while I say its not worth your time. Just do a search.

SLK
11-12-03, 07:35 PM
disable APIC

TrevGlas
11-12-03, 07:37 PM
What are the benefits of forcing IRQ's?
I can't think of any..

Sid
11-12-03, 07:37 PM
You will also need to change computer role to standard pc in device manager

aagiants
11-12-03, 08:01 PM
OK i figured out how :) i didn't know what PNP was in my bios, now i know thanks alot

TrevGlas
11-12-03, 08:20 PM
Noone answered my question. I'm just curious. Are there any benefits to forcing your IRQ's?

cyberskye
11-12-03, 11:39 PM
Read up on IRQ's - the purpose they serve and the event flow that applies.

/* hands mic to YOSC */

Some hardware plays better on it's own IRQ - so having a dedicated time-slot is advantageous. In many cases it doesn't matter. Sound cards and host adapters that require busmastering come to mind as pieces that would like 1:1.

cyberskye
11-12-03, 11:43 PM
Googled this for you - take it for what it's worth.

Cheers,

Skye

http://boards.cramsession.com/articles/files/conflicting-stories-9192003-1157.asp

Googled this for you - take it for what it's worth.

Cheers,

Skye

http://boards.cramsession.com/articles/files/conflicting-stories-9192003-1157.asp

EDIT - checked that link and requires registration - sorry :(

Google around on " IRQ steering <insert OS here> " It was a much bigger deal in the pre-98 days. The first generation of pnp was a little buggy - that's sw for ya :) I would only disable it if I had to - troubleshooting a system that wouldn't boot or would randomly hang. Since w2k it's (PnP) been part of the OS design.

YeOldeStonecat
11-13-03, 05:18 AM
///takes mic from Cyberskye, stands up on the soap box///

"Thanks Skye"

On todays motherboards, they usually support APIC (Advanced Programmable Interrupt Controller)...which gives you from 24 to even up to 64 IRQ's to use. APIC replacing the older 8259 PIC which you only had to 15 IRQ's to work with.

I on new motherboards, if you have APIC...I like it, and use it. (as long as you are using WinNT, not 9X...9X doesn't support it)

Newer OS's are much more IRQ-sharing tolerant than 9X was...but you still have IRQ on the hardware level...before the OS is booted up. And some hardware just doesn't like to be shared, although I'm running across that less and less...with so many systems coming with integrated sound and LAN.

A couple of rules of thumb that I still follow....

If you aren't using some devices, disable them in BIOS. I'm talking about mostly legacy devices, such as those old 9 pin serial COM ports, printer LPT port, even those IDE controllers if you're using a RAID card of SATA. Disabling them in BIOS, they won't use and IRQ, and the OS won't be loading them up. Less resources used. Killing COM1 will free up IRQ 4, COM2 IRQ3, LPT IRQ 7. IDE 1/2 IRQ 15/14 I believe.

Try to avoid using that top PCI slot...on most motherboards it has IRQ sharing with your AGP...video. Often some sort of sharing going on in the bottom PCI slot slot, especially on older mobo's....it would usually share an IRQ with an ISA device.

Network cards...always try to use PCI slot #2.

Some devices...if you don't want them sharing, some PCI slots on your motherboard allow you to assign them an IRQ. Like for example, when I was using my Promise RAID controller, no matter where I put it, it seemed to want to share an IRQ...even though I had freed up a bunch. So I put it in PCI slot 4 or something...and since I had freed up IRQ 3 by disabling my serial COM ports...I went into the BIOS, and assigned PCI slot 4 IRQ 3..which forced my Promise card to use that.

Benefits of forcing IRQ's, or even bothering to fiddle with them? Well, with todays new hardware, it's matured a bit compared to some of the issues we'd find even just two years ago, especially before APIC. With Win9X, and that 15 IRQ max....more and more systems were coming with more and more "stuff". As more and more options came on computers, with 15 IRQ's...naturally a lot of IRQ sharing was beginning to happen. This creates problems sometimes. Systems not shutting down, systems locking up. Sound cards were a big one....if they shared, you'd sometimes get stuttering, odd effects..while playing a game, if they shared an IRQ. Often systems didn't have any problems, they still worked fine. But due to the incredible amount of different hardware out there...all the various combinations it could be put together...now and then you did get problems. Call Creative labs for support on your sound card...IRQ's would come up, and making sure you didn't have it sharing. Call 3COM up for something about that NIC...and IRQ sharing would be asked.

IRQ's work on the hardware level, as well as in the OS. Win2K became more IRQ-sharing tolerant than 9X, but on systems with older 8259 PIC BIOS...I still found the same rules applied as did with Win9X. Just remember what an IRQ is...an interrupt request that a piece of hardware has with the CPU...basically how important it is to stand in line....and demand a response from the CPU. My belief..is you do not want important devices to share that with anyone else...you don't want squabbling between devices. Some things..who cares if they share. But other things...like IMHO video card, sound card, RAID cards, etc...you don't want to share.

I used to say "Square away your IRQ's on the hardware level first...before you even install your OS...and the OS has no choice but to follow." Back when I was running 98...I'd do that, and just never had the problems I saw peeps have with IRQ sharing and odd quirks happening. As to leaning out...I haven't done comparisons on new systems, but back when I still ran Win98, I'd run 3DMarks with all IRQ's loaded, everything turned on...then I'd shut down unused stuff...freeing up resources, she's surely run better, faster.

This question used to come up a lot on this forum, if you search back a couple of years, you'll see lots of replies I made like the above. But we don't see it much anymore. I believe that's because most new systems are running APIC....having to cram all that stuff into 15 IRQ's is no longer an issue. I glace at my Device Mangler now....I have my IRQ's spread out over 24. It's nice! It works!

Adrians Rojak Pot has a ton of excellent articles on BIOS, tweaking, IRQ's, etc. Explanations of ACPI, APIC, etc.

///scampers off to get another cup of joe///

TrevGlas
11-13-03, 08:56 AM
Nice bit of info there.

YeOldeStonecat
11-14-03, 06:23 PM
Originally posted by TrevGlas
Nice bit of info there.

:D

I've had my fun with them years ago. Couple of jobs ago...had to learn IRQ's inside and out.