Hi all,

I'm sure this eventually will be resolved with a BIOS or kernel update, but in case someone experiences this on this or a similar motherboard, I thought I'd post a problem-and-workaround report.

Platform CentOS5, x86_64 kernel-2.6.18-53.1.21.el5 Motherboard Asus M3a78-EMH HDMI SATA-controller configured as AHCI

Experienced symptom; Periodic, ~20s lockups/freezes, several a day, in conjunction with disk (SATA) I/O. Kernel logs something like this;

ata3.00: exception Emask 0x0 SAct 0x1 SErr 0x0 action 0x2 frozen ata3.00: cmd 61/08:00:71:18:7d/00:00:02:00:00/40 tag 0 cdb 0x0 data 4096 out res 40/00:00:00:4f:c2/00:00:00:4f:c2/00 Emask 0x4 (timeout) ata3: soft resetting port ata3: SATA link up 1.5 Gbps (SStatus 113 SControl 300) ata3.00: configured for UDMA/133 ata3: EH complete SCSI device sdc: 234441648 512-byte hdwr sectors (120034 MB) sdc: Write Protect is off sdc: Mode Sense: 00 3a 00 00 SCSI device sdc: drive cache: write back

(on a side note, the system has 6 SATA disks, the older ST3120827AS Seagate-disk here exhibits this significantly more often than the others, but they too are affected)

From other sources this is reported as a AHCI NCQ bug.

My workaround, which was suggested somewhere else, was to disable NCQ;

(in rc.local) for D in sd{a,b,c,d,e,f} ; do echo 1 > /sys/block/$a/device/queue_depth done

This resolves the above issue, and from several times an hour, I have not experienced it since (~30h).

Yours, -S