[READ_DMA again]

Hi all,
I know that there're many discussions about this, but I still want to take 
a note more here.
I've just cvsup and update world and kernel this afternoon.
----------------
%uname -a
FreeBSD unix.hackers 6.0-CURRENT FreeBSD 6.0-CURRENT #8: Tue Dec  7 
22:07:14 MSK 2004 
----------------
On the FreeBSD beta-6 and 5.3-REL the problems of READ_DMA, WRITE_DMA very 
often occured and many times they made the system hang! The 5.2.1 also 
met the "*_DMA" problem, but I'm sure all is okay, my computer still 
worked.
Then I decided to go on to 6.0-CURRENT, with the hope that someone will 
fix this problem. And as you see, it is not better. After producing some 
messages like:
------------
Dec  8 00:29:39 unix kernel: ad2: TIMEOUT - READ_DMA retrying (2 retries 
left) LBA=163544546
Dec  8 00:29:39 unix kernel: ad2: FAILURE - READ_DMA timed out
Dec  8 00:29:39 unix kernel: g_vfs_done():ad2s3[READ(offset=20811415552, 
length=16384)]error = 5
------------
the computer hanged immediately. Just that. Using atacontrol to turn the 
chanel to PIO4, for example, didn't help, errors like "READ_???" or 
"WRITE_???" still there, and the system will hang again.
What can be the problem here? May be it is because i put an ATA-133 HDD in 
an old  ATA66 only computer?

dmesg here:
-----------------------------------------------------------------------
%dmesg
Copyright (c) 1992-2004 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
         The Regents of the University of California. All rights reserved.
FreeBSD 6.0-CURRENT #8: Tue Dec  7 22:07:14 MSK 2004
     root_at_unix.hackers:/mnt/unix/Temp/obj/usr/src/sys/kernel
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: Intel Celeron (730.97-MHz 686-class CPU)
   Origin = "GenuineIntel"  Id = 0x686  Stepping = 6

Features=0x383fbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,MMX,FXSR,SSE>
real memory  = 267386880 (255 MB)
avail memory = 256503808 (244 MB)
npx0: [FAST]
npx0: <math processor> on motherboard
npx0: INT 16 interface
pcib0: <Intel 82815 (i815 GMCH) Host To Hub bridge> pcibus 0 on 
motherboard
pir0: <PCI Interrupt Routing Table: 9 Entries> on motherboard
pci0: <PCI bus> on pcib0
agp0: <Intel 82815 (i815 GMCH) SVGA controller> mem 
0x40300000-0x4037ffff,0x44000000-0x47ffffff irq 9 at device 2.0 on pci0
pcib1: <PCIBIOS PCI-PCI bridge> at device 30.0 on pci0
pci2: <PCI bus> on pcib1
rl0: <Accton MPX 5030/5038 10/100BaseTX> port 0x1000-0x10ff mem 
0x40000000-0x400000ff irq 5 at device 9.0 on pci2
miibus0: <MII bus> on rl0
rlphy0: <RealTek internal media interface> on miibus0
rlphy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
rl0: Ethernet address: 00:10:b5:eb:df:f7
isab0: <PCI-ISA bridge> at device 31.0 on pci0
isa0: <ISA bus> on isab0
atapci0: <Intel ICH UDMA66 controller> port 
0x2460-0x246f,0x376,0x170-0x177,0x3f6,0x1f0-0x1f7 at device 31.1 on pci0
ata0: channel #0 on atapci0
ata1: channel #1 on atapci0
pci0: <serial bus, USB> at device 31.2 (no driver attached)
pci0: <multimedia, audio> at device 31.5 (no driver attached)
cpu0 on motherboard
orm0: <ISA Option ROMs> at iomem 0xe0000-0xeffff,0xc0000-0xc7fff on isa0
atkbdc0: <Keyboard controller (i8042)> at port 0x64,0x60 on isa0
atkbd0: <AT Keyboard> irq 1 on atkbdc0
kbd0 at atkbd0
atkbd0: [GIANT-LOCKED]
fdc0: <Enhanced floppy controller> at port 0x3f0-0x3f5 irq 6 drq 2 on isa0
fdc0: [FAST]
fd0: <1440-KB 3.5" drive> on fdc0 drive 0
sc0: <System console> at flags 0x100 on isa0
sc0: VGA <16 virtual consoles, flags=0x300>
vga0: <Generic ISA VGA> at port 0x3c0-0x3df iomem 0xa0000-0xbffff on isa0
unknown: <PNP0700> can't assign resources (port)
unknown: <PNP0303> can't assign resources (port)
Timecounter "TSC" frequency 730967047 Hz quality 800
Timecounters tick every 1.000 msec
ipfw2 initialized, divert loadable, rule-based forwarding disabled, 
default to accept, logging disabled
ad0: 9541MB <Maxtor 31024H1/YAH814Y0> [19386/16/63] at ata0-master UDMA66
ad2: 117246MB <Maxtor 6Y120L0/YAR41BW0> [238216/16/63] at ata1-master 
UDMA66
kern_symlink  = 0
Trying to mount root from ufs:/dev/ad0s1a
WARNING: / was not properly dismounted

-----
With best regards,          |            The Power to Serve
Nguyen Tam Chinh            |          http://www.FreeBSD.org
Loc: sp.cs.msu.ru           |
http://chinhngt.svmgu.com   |  http://www.gnu.org/copyleft/copyleft.html