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Determining the APIC timer frequency using CPUID only
Posted: Wed Dec 11, 2024 9:47 am
by mrjbom
Since “APIC timer's frequency is equal to the bus' frequency OR the core crystal's frequency divided by the chosen frequency divider”, is it possible to get bus frequency or core crystal frequency using cpuid 0x15 and 0x16 to calculate APIC Timer's frequency and not use the PIT method described on Wiki? Is it possible? How well will it work?
Re: Determining the APIC timer frequency using CPUID only
Posted: Wed Dec 11, 2024 9:11 pm
by Octocontrabass
mrjbom wrote: ↑Wed Dec 11, 2024 9:47 amis it possible to get bus frequency or core crystal frequency using cpuid 0x15 and 0x16 to calculate APIC Timer's frequency and not use the PIT method described on Wiki?
Yes, if the CPU supports those CPUID leaves.
mrjbom wrote: ↑Wed Dec 11, 2024 9:47 amHow well will it work?
It's better than using the PIT to measure the APIC timer frequency.