choice of absolute / relative freqs with est + p4tcc

[Ian Smith]

Following a browse of the latest kern_cpu.c fixing kern/114722 and of
est.c and p4tcc.c, I notice these in the dmesg posted with kern/108954:

dev.cpu.0.freq: 225
dev.cpu.0.freq_levels: 1200/-1 1100/-1 1000/-1 900/-1 800/-1 700/-1 600/-1 525/-1 450/-1 375/-1 300/-1 225/-1 150/-1 75/-1
dev.acpi_perf.0.%driver: acpi_perf
dev.acpi_perf.0.%parent: cpu0
dev.est.0.%desc: Enhanced SpeedStep Frequency Control
dev.est.0.%driver: est
dev.est.0.%parent: cpu0
dev.est.0.freq_settings: 1200/-1 1100/-1 1000/-1 900/-1 800/-1 600/-1
dev.cpufreq.0.%driver: cpufreq
dev.cpufreq.0.%parent: cpu0
dev.p4tcc.0.%desc: CPU Frequency Thermal Control
dev.p4tcc.0.%driver: p4tcc
dev.p4tcc.0.%parent: cpu0
dev.p4tcc.0.freq_settings: 10000/-1 8750/-1 7500/-1 6250/-1 5000/-1 3750/-1 2500/-1 1250/-1

.. and find myself curious why 550 (1100 * .5) and 500 (1000 * .5)
would not be chosen when 525 (600 * .875) was, going by the comments:

	/*
	 * Walk the set of all existing levels in reverse.  This is so we
	 * create derived states from the lowest absolute settings first
	 * and discard duplicates created from higher absolute settings.
	 * For instance, a level of 50 Mhz derived from 100 Mhz + 50% is
	 * preferable to 200 Mhz + 25% because absolute settings are more
	 * efficient since they often change the voltage as well.
	 */
and 
	/*
	 * Insert the new level in sorted order.  If it is a duplicate of an
	 * existing level (1) or has an absolute setting higher than the
	 * existing level (2), do not add it.  We can do this since any such
	 * level is guaranteed use less power.  For example (1), a level with
	 * one absolute setting of 800 Mhz uses less power than one composed
	 * of an absolute setting of 1600 Mhz and a relative setting at 50%.
	 * Also for example (2), a level of 800 Mhz/75% is preferable to
	 * 1600 Mhz/25% even though the latter has a lower total frequency.
	 */

when neither 550 nor 500 (quite) match, with respect to 525:

/sys/sys/cpu.h:#define CPUFREQ_CMP(x, y)       (abs((x) - (y)) < 25)

I suspect I'm just misinterpreting something here; please clue me in?

cheers, Ian