Re: [preview] Latest AMD & VIA IDE drivers with UDMA100 support

[Alan Chandler]

On Sat, 20 Jan 2001 14:57:07 -0800 (PST), Andre Hedrick wrote:

...
>
>Vojtech, I worry that the dynamic timing that you are calculating could
>bite you.  Timings are exact especially at modes 3/4/5 the margins go to
>an effective zero for varition or wiggle room.  The state diagrams from
>Quantum that created the Ultra DMA 0,1,2,3,4,5 show how darn tight it
>constrained.  You need to assume absolutes because the various board
>makers screw up the skew tables by the PCB lane traces.
>

I am not sure this is just a question of small variations.  The hdparm
-t differences between these two versions is quite significant.  This
evidence would imply that the two approaches are making fundemental
different decisions about what my hardware can do!

Under 2.2.17

/dev/hda:
 Timing buffered disk reads:  64 MB in 21.86 seconds =  2.93 MB/sec

/dev/hdc:
 Timing buffered disk reads:  64 MB in 20.81 seconds =  3.08 MB/sec

Under 2.4.0

/dev/hda:
 Timing buffered disk reads:  64 MB in  6.58 seconds =  9.73 MB/sec

/dev/hdc:
 Timing buffered disk reads:  64 MB in  6.59 seconds =  9.71 MB/sec

Alan

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