Harddisk speed: PIO4 vs. UDMA66 controller ?

[Rob]

Hi,


I have a PII PC running 5.3. The output of 'dmesg' has a line:

  atapci0: <VIA 82C596B UDMA66 controller> [...] at device 7.1 on pci0

And at the end, it says:

  ad0: 43979MB <IBM-DTLA-307045/TX6OA50C> [89355/16/63] at ata0-master PIO4
  acd0: CDROM <CRD-8520B/1.00> at ata1-master PIO4

The harddisk is very new and can do UDMA100. With a UDMA66 controller
I expect the harddisk to operate at least at 66 MB/sec. Any ideas why
the speed is only PIO4?

Having a UDMA100 harddisk, working at PIO4 is too much of a pity, but
66 MB/sec would be OK.

Thanks,
Rob.