Higher ATA-Mode -> lower speed

[Emanuel Strobl]

Dear ata interested guys,

I observed a strange behaviour which seems to explain my often noticed "16MB/s 
hard-limit"

I have a UDMA133 drive (MAXTOR 6L060J3) which saturates at 16MB/s when I dump 
anything to it, regardless of the block size. This transfer rate is reached 
with bs=4k and doesn't increase any more even not with bs=64k.

Now, when I set the mode to UDMA100 I get well over 40MB/s!!!!

Can anybody confirm that for different hw? Especially people like fandino who 
already discussed poor ata performance on -current (~16 Oct. 04).

Why does UDMA133 mode limit the transfer speed so badly? And why do I get 
significantly slower transfer rates (32MB/s insted of 42MB/s) when I set the 
mode to UDMA66 (compared to UDMA100 but twice the speed of UDMA133)? There's 
only one device on the channel, so UDMA66 should be fine for 42MB/s.
The controller is a HPT372.

Best regards,

-Harry
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