Re: ahcisata usage mode (on NetBSD 6.1.1 (GENERIC) amd64)

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Sat, Sep 28, 2013 at 10:35:16AM +0200, Job Hanssen wrote:
> [...]
> wd4 at atabus4 drive 0
> wd4: <WDC WD10EAVS-00D7B0>
> wd4: drive supports 16-sector PIO transfers, LBA48 addressing
> wd4: 931 GB, 1938021 cyl, 16 head, 63 sec, 512 bytes/sect x 1953525168
> sectors
> wd4: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133)
> wd4(ahcisata0:4:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 6
> (Ultra/133) (using DMA)
> 
> >From the "(using DMA)" in the last line for each drive, I undertand that
> I'm currenctly running DMA mode 2. Am I correct?

No, it's really using the hightest (U)DMA mode available. The "using DMA"
is just there to mention that when possible it won't use PIO to transfer
data.
ATA has 2 way to transfer data: PIO and DMA, with different commands.
Ultra-DMA is just a sub-class of DMA and the same commands will do
either DMA or Ultra-DMA, depending on what's available.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--