regression in ata/atapi wrt dma?
q at uni.de
Sat Sep 25 08:13:16 PDT 2004
On Sun, 19.09.2004 at 17:17:50 +0200, Søren Schmidt wrote:
> This is the "new worldorder" for ATAPI devices. The default is now to
> enable DMA if the device claims to support at least UDMA33, if not its
> left in PIO mode. This is to avoid all the (old) sucky devices that
> claims DMA but really doesn't work.
> If you need any modes beyond this, please use atacontrol.
I guess something like this is needed then...
--- ata.4.orig Wed Sep 22 10:34:19 2004
+++ ata.4 Wed Sep 22 11:11:32 2004
@@ -86,7 +86,7 @@
.It Va hw.ata.ata_dma
set to 1 for DMA access, 0 for PIO (default is DMA).
.It Va hw.ata.atapi_dma
-set to 1 for DMA access, 0 for PIO (default is PIO).
+set to 1 for DMA access, 0 for PIO (default is DMA, if the drive supports at least UDMA33).
.It Va hw.ata.wc
set to 1 to enable Write Caching, 0 to disable (default is enabled).
.Em WARNING :
@@ -161,8 +161,10 @@
or that one of the devices on the channel only accepts up
-ATAPI devices are set to PIO mode by default because severe DMA problems are
-common even if the device capabilities indicate support.
+ATAPI devices are set to DMA mode only if they claim to support at least UDMA33.
+Older devices claiming DMA or WDMA support get set to PIO by default because
+severe DMA problems are common even if the device capabilities indicate
You can always try to set DMA mode on an ATAPI device using
.Xr atacontrol 8 ,
but be aware that your hardware might
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