[plug] APIC

Craig Ringer craig at postnewspapers.com.au
Wed Jun 30 12:05:57 WST 2004


Cameron Patrick wrote:
> Michael Holland wrote:
> 
> | But what does it do?  OK, it controls interrupts, but whats the
> | alternative? What do I loose by disabling it?
> 
> The alternative is the plain PIC that has been around since the XT,
> which has a limited number of interrupts.  When you have too many
> devices attached, they have to share interrupts which is slower (I
> think).

Interrupt sharing can also cause problems with buggy PCI cards / drivers 
- the Sound Blaster Live comes to mind as something I've found to be a 
regular offender when sharing interrupts.

In general, I find that the IO-APIC just makes life easier. No IO-APIC 
is much better than a buggy IO-APIC any day, though. Unless you're on an 
SMP machine, of course, where you _need_ an IO-APIC.

You may be interested to note that Microsoft forced chipset and 
motherboard manufacturers into including IO-APICs as standard. Perhaps 
it was out of frustration at all the driver and hardware problems caused 
by the shortage of interrupt lines that were being blamed on Windows. 
Whatever - it's mighty handy for everybody, unlike other Microsoft 
hardware initiatives like BIOS splash screens.

--
Craig Ringer
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