Abit KV-80 mobo: cpu fan shows correct RPMs, other two fan..

Have an ABIT KV-80. Flashed to latest (-17) bios. Three fans are
plugged into the fan headers:

AMD's included CPU fan to "CPUFAN" header
Thermaltake chipset fan to "NBFAN" header
Enermax PS fan lead to "SYSFAN" header.

Only the CPUfan shows RPMs when I go into the BIOS's "PC Health"
screen. The other two report zero. Huh? But I can see them spinning...

*ALL THREE FANS* are three-wire types that should be able to report
speed...in fact that's the ONLY thing the power supply fan lead is
there for, to monitor the fan, not to power it.

Any ideas on what's wrong here? Is the Abit just not getting the
readings? Is there anything I can try?

thanks for any info or just random speculation,
jon