why does UATA/133 == UATA/100 on amd64?

[Alexander Motin]

Peter Jeremy wrote:
> On 2010-Jun-04 16:36:08 -0700, fbsdmail at dnswatch.com wrote:
>> After _finally_ making the correct decisions to install amd64 on an
>> AMD64 system. I was able to make/build/install world && kernel, I see
>> a difference in drive recognition.
> 
> Can you please do a verbose boot and post the resultant dmesg somewhere
> (preferably with your USB DVD drive connected).
> 
>> kernel: ata3-master: pio=PIO4 wdma=WDMA2 udma=UDMA133 cable=40 wire
>> kernel: ad6: 476940MB <Seagate ST3500630AS 3.AAK> at ata3-master SATA300
> 
>> kernel: ata3-master: pio=PIO4 wdma=WDMA2 udma=UDMA133 cable=40 wire
>> kernel: ad6: setting UDMA100
>> kernel: ad6: 476940MB <Seagate ST3500630AS 3.AAK> at ata3-master UDMA100
>> SATA 3Gb/s
> 
> The 'UDMA' numbers are meaningless for SATA controllers/drives.

The 'UDMA' numbers are meaningless for _native_ SATA controllers/drives.

They may be not meaningless for legacy SATA devices, using SATA->PATA
bridge inside. Some bridges do not support UDMA133 on PATA part, so
ata(4) prefers not to use it. But in this case it is indeed meaningless.

-- 
Alexander Motin