Guennadi Liakhovetski wrote:
> Hi
> > will try tonight... and will let you know tomorrow...
> ... Nop, it didn't work. Mike and everybody having experience / knowledge of Western
>Digital Caviar AC21600H... If you compare WD's documents at:
> http://www.westerndigital.com/service/FAQ/dtr.html
> and
> http://www.westerndigital.com/products/non-current/drives/ac21600.html
> they, respectively ,say:
>
> UDMA if CCC is A8-AG (AH is not UDMA), D5-D7, Bx, or Cx All others -- PIO Mode 4
>
> and
>
> 16.6 MB/s (burst Mode 4 PIO) *
> 16.6 MB/s (burst Mode 2 DMA) **
> 33.3 MB/s (Mode 2 Ultra DMA) ***
>
> *Max PIO burst rate is specified at 16.6 MB/s using the IORDY signal.
> **Max DMA and multi-word DMA burst rate is specified using the DMARQ and DMACK
>signals.
> ***Mode 2 Ultra DMA is supported in the following firmware revisions (CCC Codes: A8,
>AA, AC, AD, AG, D5, D6, D7, Bx, Cx).
>
> Which one is true? Do non-UDMA AC21600H (I've got CCC F6) support DMA?
>
> Is it possible to find out where hdparm -d1 is stopped? Maybe by compiling it with
>-g and debugging... As far as I understand, BIOS is not an issue, since ide.txt says,
>that Linux doesn't use BIOS when working with hard drives...
>
> Thanks
> Guennadi
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Well, per my other email, i found a case where the bios DID matter. Yes, the AC21600H
supports DMA. Even my dinosaur 850 meg in that same box, works in dma mode, and does
get a little bit faster. They're so slow in the first place
that it doesn't make much transfer rate difference, but the cpu load goes way down.
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