I am seeing this:

sd0(ahc0:0:0): data overrun of 500 bytes detected.  Forcing a retry.
sd0(ahc0:0:0): data overrun of 500 bytes detected.  Forcing a retry.

just recently, which is messing up my filesystems a
bunch. --:(  [inodes get weird data stuffed into them mostly]

ahc0 at pci0 dev 8 function 0
ahc0: interrupting at irq 9
ahc0: aic7880 Wide Channel, SCSI Id=7, 16 SCBs
scsibus0 at ahc0 channel 0: 16 targets
ahc0: target 0 using 16Bit transfers
ahc0: target 0 synchronous at 20.0MHz, offset = 0x8
sd0 at scsibus0 targ 0 lun 0: <QUANTUM, XP34550W, LYK8> SCSI2 0/direct fixed
sd0: 4341MB, 5899 cyl, 10 head, 150 sec, 512 bytes/sect x 8890760 sectors

I think it might be related to:

mjacob
Sat Jul  4 15:29:46 PDT 1998
Update of /cvsroot/src/sys/dev/microcode/aic7xxx
In directory nb00:/tmp/cvs-serv7707

Modified Files:
        aic7xxx.seq aic7xxx_seq.h 
Log Message:
port-i386/5706: I had no problem with the previous patch, but someone
else has. Rolling it back while we try and figure it out.

and

mjacob
Fri Jul  3 16:45:11 PDT 1998
Update of /cvsroot/src/sys/dev/microcode/aic7xxx
In directory nb00:/tmp/cvs-serv4163

Modified Files:
        aic7xxx.seq aic7xxx_seq.h 
Log Message:
Patches from Justin that handle some REV B AIC7880 problems

mjacob
Fri Jul  3 16:45:33 PDT 1998
Update of /cvsroot/src/sys/dev/ic
In directory nb00:/tmp/cvs-serv4193

Modified Files:
        aic7xxxreg.h 
Log Message:
Patches from Justin that handle some REV B AIC7880 problems

	Sean.