local apic disabled

slinky2004 · 10-21-2005, 02:41 PM

when i look at dmesg i see this entry:

Code:

Local APIC disabled by BIOS -- you can enable it with "lapic"

i've enabled "Local APIC support on uniprocessors" in my kernel, and i've been told that enabling local apic in my bios will make this work, but my bios is really basic and there isnt anything in there to enable apic. does this mean my computer(its a sony vaio, btw) doesn't have an apic controller? i couldnt find out if i had a local apic controller using google and the sony website. in case i dont have local apic, what are the consequences of this? does it make that much difference?

Moloko · 10-21-2005, 03:13 PM

APIC enables more IRQ addresses (24 instead of 12?). I had to use an unofficial K7 BIOS to get it working and it seemed to make Linux slightly faster without IRQ sharing.

If you don't have the option in the BIOS you can't use APIC. You're not missing out on something big ;-)

slinky2004 · 10-21-2005, 05:38 PM

k, thx

nelamvr6 · 10-22-2005, 03:22 AM

That's good to know!

Coming from the Windows / overclocking world, APIC is really discouraged there!

Can I simply enable it in my BIOS and enjoy faster speeds or will that involve a recompiling of the kernel?

grolich · 11-08-2005, 01:18 PM

Has anyone ever used interrupts that are generated on LOCAL APIC (like the Performance monitor interrupt, which I'm trying to use)?

I've enabled support for local apic in the kernel.
it seems that now the kernel recognizes 256 interrupts (at least that's the what /proc/stat says...
It didn't before),

but how do I write and register the interrupt handler for it?

I cannot seem to register it normally with request_irq because on all non busy interrupts,
I get a ENOSYS error...
any ideas?