Harddisk speed: PIO4 vs. UDMA66 controller ?

[Rob]

Rob wrote:
> 
> 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?

I just realize that I have put in /boot/loader.conf:

   hw.ata.ata_dma="0"

to prevent a WRITE_DMA panic at bootup.
That's probably the reason why the harddisk speed is forced
to PIO4, right?

This 'WRITE_DMA' problem, is causing trouble on several other
of my PCs here. This is quite a nuissance with 5.3 !

Rob.