ACPI slowing CPU... or something else

[V.I.Victor]

 I've two 5.4 desktop boxes.  Pretty much the same installation; both
 from the same CD, same apps, no monitor/keyboard, 1-user logged-on via
 ssh (command-line only w/no gui) and otherwise lightly loaded.

 Box_A: CPU: AMD-K7(tm) Processor (598.84-MHz 686-class CPU)
        avail memory = 121630720 (115 MB)
        ACPI disabled by blacklist.

 Box_B: CPU: Intel(R) Pentium(R) 4 CPU 1.80GHz (1794.19-MHz 686-class CPU)
        avail memory = 252186624 (240 MB)
        cpu0: <ACPI CPU> on acpi0
        acpi_throttle0: <ACPI CPU Throttling> on cpu0

 When running the following segment of a small gawk program:

     cnt=0; s=systime(); while(s==systime()) ; # next second
     s=systime(); while(s==systime()) cnt++; # count for 1-sec

 Box_A(600M) always reports 'cnt' between 310000 to 320000.

 Box_B(1800M) has been as low as 167000 and never higher than 254000.

 So -- Box_B is 3-times faster than Box_A but runs the segment (at
 best) about 20% more slowly!

 Yesterday was when I saw the Box_B(1800M) 167000-ish numbers.  Today
 after seeing an increase to the 250000-ish numbers, I started to
 read-up on ACPI.

 sysctl -a | grep cpu.*freq reports:

 dev.cpu.0.freq: 1796
 dev.cpu.0.freq_levels: 1796/-1 1571/-1 1347/-1 1122/-1 898/-1 \
                        673/-1 449/-1 224/-1
 dev.cpufreq.0.%driver: cpufreq
 dev.cpufreq.0.%parent: cpu0

 If I understand the 'sysctl' output, Box_B is running (now) at
 1796-MHz.  And for Box_B cnt==252433; for Box_A cnt==318942.

 Any opinions on what's going on and/or what I'm not understanding?

 Thanks!