IRQ sharing (assignments) slow down GFX card?

[gwolfman]

Hi,

I was looking at my manual for my ASUS P5Q-E motherboard and noticed this, the highlighted parts in particular:

Now my understanding of IRQs is that any device with the same IRQ has to share CPU time since they have to take turns. So, for example, if I have a sound card installed on PCI_1, does that limit how much CPU time that my graphics card on PCIE16_1 gets? If so, is the difference so small it won't matter or can it have a measurable affect?

Any info would be greatly appreciated. Thanks.
-GWolfman

 

[slicessoul]

With current mainboard, i think this is not an issue anymore

The reason why it's using a shared IRQ : http://www.patentstorm.us/patents/7200700/description.html

the invention provides a shared-IRQ user-defined interrupt signal
handling method and system for use with a computer platform to allow a
group of peripheral devices connected to an interrupt-configurable
peripheral interface to
share system interrupt lines IRQ with
another group of peripheral devices connected to an interrupt
nonconfigurable peripheral interface, and which is characterized by the
provision of an interrupt configuration table for defining a virtual
device for
the interrupt-configurable peripheral interface as well
as each specific system interrupt line that is shared by the two groups
of peripheral devices. This feature allows system interrupt lines IRQ
to be shared by the peripheral devices connected to the
interrupt-configurable
peripheral interface and the peripheral devices connected to the
interrupt-nonconfigurable peripheral interface, and also allows the
implementation to be easier to carried out than prior art without
involving complex and difficultBIOS coding.

In Windows XP, Device Manager may list some or all the devices on your
ACPI motherboard as using the same IRQ (IRQ 9). (To view the list of
resources, click either Resources by type or Resources by connection on the View

menu). No option is available to change the IRQ setting. Windows takes
advantage of the ACPI features of the motherboard, including advanced
PCI sharing. The PCI bus uses IRQ 9 for IRQ steering. With this
feature, you can add more devices without IRQ conflicts.

source: Microsoft http://support.microsoft.com/kb/314068
No IRQ conflicts means no problem.

 

[gwolfman]

Wow, very interesting and informative. Thanks for the detailed information and links.