Core2Duo: Move to\from C4 state

[zvivered]

Hello,

I want to put Core2Duo into C4 state under vxWorks 6.8
So I ran the following code:

Code: Select all

mov EAX, 0x30 (Bits 0-3 define C4 sub state. What sub state shoud I use ?)
mov ECX, 0x0 
mwait

But it seems nothing happenes. Because the system clock is running every 1ms, the CPU is put back to C0
How can I configure the CPU to go back to C0 upon an APIC timer (for example) and not any other interrupt ?
Where can I find documentation on C4 sub states ?

Thanks,
Zvika.