problem with UDMA mode on XP1000

[Jarkko Santala]

On Wed, 16 Apr 2003, Andrew Gallatin wrote:

> Jarkko Santala writes:
>  > On Tue, 15 Apr 2003, Jameel Akari wrote:
>  >
>  > > 	I had the same sort of problem in an Alpha PC164, but in the end
>  > > the onboard IDE was so terrible and Tru64 refused to run a hard disk on
>  > > it, so I bought an ISP1040 and went SCSI, and it's been solid.
>  >
>  > Well, I don't think it's that terrible:
>  >
>  > dd if=/dev/zero of=foo bs=1m count=100:
>  > ad0: 104857600 bytes transferred in 6.863760 secs (15276991 bytes/sec)
>  > da0: 104857600 bytes transferred in 8.200968 secs (12786003 bytes/sec)
>  >
>  > atapci0: <CMD 646 ATA controller> port 0x10180-0x1018f irq 5 at device 11.0 on pci0
>  > ad0: 117246MB <Maxtor 4G120J6> [238216/16/63] at ata0-master WDMA2
>
> FWIW, WDMA2 is not safe as there is no CRC checking.  I've seen
> corrupted (random, infrequent single bit errors) files when running a
> PC164LX with an ata drive in WDMA2 mode.  The higher modes (UDMA33 ..)
> get you CRC checking.  As soon as we noticed the corruption, we moved
> the box to SCSI.

I suppose no checking explains the performance. ;) But good to know
anyway. Any reason why it gets enabled by default if its not safe?

	-jake

-- 
Jarkko Santala <jake at iki.fi>            http://www.iki.fi/~jake/
System Administrator                    2001:670:83:f08::/64