Timecounter quick question regarding ACPI-safe and ACPI-fast

E

einthusan

I have 2 machines, both with the same processor.

Machine 1
Code: 
kern.timecounter.choice: TSC-low(1000) [B]ACPI-safe(850)[/B] i8254(0) dummy(-1000000)
kern.timecounter.hardware: TSC-low
kern.timecounter.stepwarnings: 0
kern.timecounter.tc.i8254.mask: 65535
kern.timecounter.tc.i8254.counter: [B]36426[/B]
kern.timecounter.tc.i8254.frequency: 1193182
kern.timecounter.tc.i8254.quality: 0
kern.timecounter.tc.ACPI-[B]safe.mask[/B]: 16777215
kern.timecounter.tc.ACPI-[B]safe.counter[/B]: 11290953
kern.timecounter.tc.ACPI-[B]safe.frequency[/B]: 3579545
kern.timecounter.tc.ACPI-[B]safe.quality[/B]: 850
kern.timecounter.tc.TSC-low.mask: 4294967295
kern.timecounter.tc.TSC-low.counter: [B]1536880578[/B]
kern.timecounter.tc.TSC-low.frequency: [B]10390820[/B]

Machine 2
Code: 
kern.timecounter.choice: TSC-low(1000) ACPI-fast(900) i8254(0) dummy(-1000000)
kern.timecounter.hardware: TSC-low
kern.timecounter.stepwarnings: 0
kern.timecounter.tc.i8254.mask: 65535
kern.timecounter.tc.i8254.counter: 4387
kern.timecounter.tc.i8254.frequency: 1193182
kern.timecounter.tc.i8254.quality: 0
kern.timecounter.tc.ACPI-fast.mask: 16777215
kern.timecounter.tc.ACPI-fast.counter: 8433834
kern.timecounter.tc.ACPI-fast.frequency: 3579545
kern.timecounter.tc.ACPI-fast.quality: 900
kern.timecounter.tc.TSC-low.mask: 4294967295
kern.timecounter.tc.TSC-low.counter: 3931457100
kern.timecounter.tc.TSC-low.frequency: 10390848

Why is there such discrepancy when both machines are 99% the same?
 
Some ACPI timer implementations have a bug, that requires special handling. System tries to detect it during boot and respectively provides either fast or safe handlers.
 
mav@ said:
Some ACPI timer implementations have a bug, that requires special handling. System tries to detect it during boot and respectively provides either fast or safe handlers.
Click to expand...

Is the timer dependent on the CPU or some other hardware on the motherboard? Is it possible that the system using ACPI-safe has defected hardware? I assume overall system performance is affected by which timer is selected?

Should I be using HPET instead? Is a kernel rebuild required in order for HPET to show up in kern.timecounter.choice? I am using the GENERIC kernel, maybe I should rebuild it specifically for the processor which I am using?
 
einthusan said:
Is the timer dependent on the CPU or some other hardware on the motherboard? Is it possible that the system using ACPI-safe has defected hardware? I assume overall system performance is affected by which timer is selected?
Click to expand...

It is more to motherboard then to CPU. ACPI doesn't specify where exactly this timer is implemented, but most likely in chipset. Yes, performance may vary, but not dramatically.

einthusan said:
Should I be using HPET instead? Is a kernel rebuild required in order for HPET to show up in kern.timecounter.choice? I am using the GENERIC kernel, maybe I should rebuild it specifically for the processor which I am using?
Click to expand...

If HPET would be detected, you would see it there automatically. Check your BIOS settings to be sure it is not just disabled there.
 
mav@ said:
It is more to motherboard then to CPU. ACPI doesn't specify where exactly this timer is implemented, but most likely in chipset. Yes, performance may vary, but not dramatically.



If HPET would be detected, you would see it there automatically. Check your BIOS settings to be sure it is not just disabled there.
Click to expand...

Thanks!
 
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