Dan Strick strick at
Fri Jan 2 18:22:33 PST 2004

On Fri, 2 Jan 2004, Daniel Ortiz wrote:
 > I've a 'tyan i875p (s5102)' motherboard (with SATA 150), with a FreeBSD
 > 4.9-STABLE installed, the kernel detects the hardware fine.
 > The cable it's a fully working serial ata cable.
 > ...
 > But atacontrol always says me that it uses UDMA33 instead of SATA-150 or
 > other (I can't set UDMA66/100/133/150), in bios I tried to use legacy,
 > combined and enhaced modes but always work in UDMA33.
 > ad0: DMA limited to UDMA33, non-ATA66 cable or device
 > ad1: DMA limited to UDMA33, non-ATA66 cable or device
 > Iozone, bonnie and bonnie++ always report a maximum transfer of
 > 32MB/Sec.
 > The question is: How I can set the transfer to any other UDMA? FreeBSD
 > detects ther hardware but I can't use that features without ATAng? Any
 > patch/solution/idea?

The 4.9-STABLE driver does not particularly understand Serial ATA, but
this is not a problem here.  If the driver configures your SATA drive
for any kind of dma (e.g. UDMA33), your particular SATA controller (on
the ICH5 chip in the Intel 875P cpu support chipset) will do dma at
SATA150 dma rates.

I don't know why your I/O benchmarks report only 32 MB/sec.  Perhaps
this is natural for these benchmarks and your particular drives.
You might try "dd if=/dev/ad0 of=/dev/null bs=128k" while running
"iostat 5".  (The 128k buffer size may be necessary.)  I get about
56 MB/sec even though the driver thinks it has configured the drive
for UDMA33.

Dan Strick
strick at

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