IRQ sharing

[Bented]

Hi,

In my Asus VII Formula motherboard manual it shows a section showing IRQ Assignments and what is shared.
I have my graphics card in the main PCI-E x16 slot that is recommended.
If I was to place something in the bottom PCI-E X1 slot how do I know if performance would be impacted due to IRQ sharing?
I don't really understand exactly what the motherboard manual is showing me.

Can anyone help me understand what it means?

So at the moment I have PCIe x16/x8_1 and PCIe_x1_3 populated.

 

[YouWhat]

There are a limited number of IRQ (Interupt ReQuest) channels, and IRQ sharing is taken care of via bios (for basic assignments) the chipset (for switching) and CPU (for task handling). The basic run down for this is that it sends signals and data to the CPU for data processing and handling (eg memory swap and reading and loading etc).

I can't remember the specific channel thing of the graphics card off top of head (think it was 10 or 12) but at the speed which the FSB (Front Side Bus which basically is the speed bits on motherboard talk to each other eg CPU <-> Memory <-> CPU, CPU <-> Gfx Card etc) talk to each other is fast enough so as there is no noticable depreciation of performance to the end user.

There has to be this sharing as there are only a limited number of IRQ slot available, and for reasons I can not remember properly but something to do with mapping of he base memory (640k), extended memory (the stuff you plug in motherboard (eg 16GB ) and CPU was at the limit at which they are able to provide down on a basic hardware level, which it has to be as this happens before any OS etc is involved, so newer or more channels can not be made to fill the void that is needed with more hardware.

Each IRQ slot has a specific memory allocation assigned to it eg #001123FFE3 - #0011EEFFFF, this is then taken out of the base memory, so once that base memory slots are filled, no more can be added.

Hope this kind of makes sense to you, but it is basically no real difference from where you are sitting to what happens even if you filled all PCI / PCI-E slots and drives etc.

(Its early morning and I not had my caffine intake yet so this might not make much sense but the essential reason are there but the performance wont be effected for you)

 

[Bented]

Hi,

And thanks a million for taking the time to explain it.
Really appreciate it.

 

[RamboOC]

There are a limited number of IRQ (Interupt ReQuest) channels, and IRQ sharing is taken care of via bios (for basic assignments) the chipset (for switching) and CPU (for task handling). The basic run down for this is that it sends signals and data to the CPU for data processing and handling (eg memory swap and reading and loading etc).

I can't remember the specific channel thing of the graphics card off top of head (think it was 10 or 12) but at the speed which the FSB (Front Side Bus which basically is the speed bits on motherboard talk to each other eg CPU <-> Memory <-> CPU, CPU <-> Gfx Card etc) talk to each other is fast enough so as there is no noticable depreciation of performance to the end user.

There has to be this sharing as there are only a limited number of IRQ slot available, and for reasons I can not remember properly but something to do with mapping of he base memory (640k), extended memory (the stuff you plug in motherboard (eg 16GB ) and CPU was at the limit at which they are able to provide down on a basic hardware level, which it has to be as this happens before any OS etc is involved, so newer or more channels can not be made to fill the void that is needed with more hardware.

Each IRQ slot has a specific memory allocation assigned to it eg #001123FFE3 - #0011EEFFFF, this is then taken out of the base memory, so once that base memory slots are filled, no more can be added.

Hope this kind of makes sense to you, but it is basically no real difference from where you are sitting to what happens even if you filled all PCI / PCI-E slots and drives etc.

(Its early morning and I not had my caffine intake yet so this might not make much sense but the essential reason are there but the performance wont be effected for you)

I always what what the irq settings in bios did. Thanks for thorough explanation!

 

[YouWhat]

Thats what you get for being old school pc builder, having to know all the stuff like that to make a PC work, it used to be a nightmare sometimes trying to get the IRQ stuff set right, and then for no apparent reason it would go AWOL, esp if there was power cut, since they auto assigned and did the sharing on it (never used to be able to share IRQ's and it used to drive people to brink of insanity sometimes as cheaper hardware tended to just used whatever they wanted sometimes instead of the proper IRQ channels).

I glad to be able to try and explain how it works, always happy to try and enlighten people with my sometimes useless knowledge

 

[Wraith]

Thats what you get for being old school pc builder, having to know all the stuff like that to make a PC work, it used to be a nightmare sometimes trying to get the IRQ stuff set right, and then for no apparent reason it would go AWOL, esp if there was power cut, since they auto assigned and did the sharing on it (never used to be able to share IRQ's and it used to drive people to brink of insanity sometimes as cheaper hardware tended to just used whatever they wanted sometimes instead of the proper IRQ channels).

I glad to be able to try and explain how it works, always happy to try and enlighten people with my sometimes useless knowledge

Those were the days :lol: Win 3.1, 3.11, 95, 98. Installing a Adlib, SB16 or Matrox graphics card to have it bum out the moment you reboot.

 

[YouWhat]

Those were the days :lol: Win 3.1, 3.11, 95, 98. Installing a Adlib, SB16 or Matrox graphics card to have it bum out the moment you reboot.

Yeah, you see people getting stressed with todays hardware, and you think back to those days, they have no idea how easy they have it

Self taught master classes in PC diagnostics, if you didn't learn it for yourself, then some joe bloggs down at discounted wallet emptiers PC ltd used to lighten your bank account for you for no extra charge :lol: