Aha, thanks!
Here's the output:
sysctl kern.timecounter
sysctl kern.timecounter kern.timecounter.tick: 1 kern.timecounter.choice: TSC(-100) HPET(900) ACPI-fast(1000) i8254(0) dummy(-1000000) kern.timecounter.hardware: ACPI-fast kern.timecounter.stepwarnings: 0 kern.timecounter.tc.i8254.mask: 65535 kern.timecounter.tc.i8254.counter: 4775 kern.timecounter.tc.i8254.frequency: 1193182 kern.timecounter.tc.i8254.quality: 0 kern.timecounter.tc.ACPI-fast.mask: 4294967295 kern.timecounter.tc.ACPI-fast.counter: 976318787 kern.timecounter.tc.ACPI-fast.frequency: 3579545 kern.timecounter.tc.ACPI-fast.quality: 1000 kern.timecounter.tc.HPET.mask: 4294967295 kern.timecounter.tc.HPET.counter: 3457380201 kern.timecounter.tc.HPET.frequency: 14318180 kern.timecounter.tc.HPET.quality: 900 kern.timecounter.tc.TSC.mask: 4294967295 kern.timecounter.tc.TSC.counter: 1185842065 kern.timecounter.tc.TSC.frequency: 2695108768 kern.timecounter.tc.TSC.quality: -100 kern.timecounter.smp_tsc: 0 kern.timecounter.invariant_tsc: 1sysctl kern.hz
kern.hz: 1000Edit: I've now tried setting kern.timecounter.hardware to HPET, TSC, i8254, and ACPI-fast manually and rebooting after each (in /etc/sysctl.conf). None of the settings have been any better than the other. The instant I use something that takes a lot of bandwidth (I have a 100/10 connection) the clock goes shooting off into hyperspeed.