Hi,

I get one of these every time I use my ancient cdwriter, 
but I only use it infrequently, and it seems to work 
okay after downgrading (see end of dmesg output below).  
I also see this error very occasionally, not even once 
a month, with respect to one of my hard disks.  It 
happens only during periods of intense disk activity, 
such as when rebuilding -current.  Sometimes there 
will be two of these errors immediately following 
one another, in which case I will see the same block 
numbers.  I think once there were three in a row.  

Here is dmesg output:

NetBSD 1.6U (GENERIC) #2: Sun Jul  6 21:55:21 EDT 2003
	root@aluminum.miller.net:/usr/obj/sys/arch/i386/compile/GENERIC
total memory = 255 MB
avail memory = 229 MB
using 3296 buffers containing 13184 KB of memory
BIOS32 rev. 0 found at 0xfb2a0
mainbus0 (root)
cpu0 at mainbus0: (uniprocessor)
cpu0: VIA C3 Samuel 2/Ezra (686-class), 798.03 MHz, id 0x678
cpu0: features 80803035<FPU,DE,TSC,MSR,MTRR>
cpu0: features 80803035<PGE,MMX>
cpu0: features 80803035<3DNOW>
pci0 at mainbus0 bus 0: configuration mode 1
pci0: i/o space, memory space enabled, rd/line, rd/mult, wr/inv ok
pchb0 at pci0 dev 0 function 0
pchb0: VIA Technologies VT82C691 (Apollo Pro) Host-PCI (rev. 0xc4)
agp0 at pchb0: aperture at 0xd0000000, size 0x10000000
ppb0 at pci0 dev 1 function 0: VIA Technologies VT82C598 (Apollo MVP3) CPU-AGP Bridge (rev. 0x00)
pci1 at ppb0 bus 1
pci1: i/o space, memory space enabled
vga1 at pci1 dev 0 function 0: Nvidia Corporation RIVA TNT2 Model 64 (rev. 0x15)
wsdisplay0 at vga1 kbdmux 1: console (80x25, vt100 emulation)
wsmux1: connecting to wsdisplay0
pcib0 at pci0 dev 7 function 0
pcib0: VIA Technologies VT82C686A (Apollo KX133) PCI-ISA Bridge (rev. 0x40)
pciide0 at pci0 dev 7 function 1: VIA Technologies VT82C686A (Apollo KX133) ATA100 controller
pciide0: bus-master DMA support present
pciide0: primary channel configured to compatibility mode
wd0 at pciide0 channel 0 drive 0: <WDC WD800JB-00CRA1>
wd0: drive supports 16-sector PIO transfers, LBA addressing
wd0: 76319 MB, 16383 cyl, 16 head, 63 sec, 512 bytes/sect x 156301488 sectors
wd0: 32-bit data port
wd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 5 (Ultra/100)
wd1 at pciide0 channel 0 drive 1: <SAMSUNG SW0212A (2.1GB)>
wd1: drive supports 16-sector PIO transfers, LBA addressing
wd1: 2014 MB, 4092 cyl, 16 head, 63 sec, 512 bytes/sect x 4124736 sectors
wd1: 32-bit data port
wd1: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 2 (Ultra/33)
pciide0: primary channel interrupting at irq 14
wd0(pciide0:0:0): using PIO mode 4, Ultra-DMA mode 5 (Ultra/100) (using DMA data transfers)
wd1(pciide0:0:1): using PIO mode 4, Ultra-DMA mode 2 (Ultra/33) (using DMA data transfers)
pciide0: secondary channel configured to compatibility mode
atapibus0 at pciide0 channel 1: 2 targets
cd0 at atapibus0 drive 0: <HP      CD-Writer+ 7200, 4VO0998371600200021, V:003.0> cdrom removable
cd0: 32-bit data port
cd0: drive supports PIO mode 3, DMA mode 1
pciide0: secondary channel interrupting at irq 15
cd0(pciide0:1:0): using PIO mode 3, DMA mode 1 (using DMA data transfers)
uhci0 at pci0 dev 7 function 2: VIA Technologies VT83C572 USB Controller (rev. 0x16)
uhci0: interrupting at irq 11
usb0 at uhci0: USB revision 1.0
uhub0 at usb0
uhub0: VIA Technologies UHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub0: 2 ports with 2 removable, self powered
uhci1 at pci0 dev 7 function 3: VIA Technologies VT83C572 USB Controller (rev. 0x16)
uhci1: interrupting at irq 11
usb1 at uhci1: USB revision 1.0
uhub1 at usb1
uhub1: VIA Technologies UHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub1: 2 ports with 2 removable, self powered
pchb1 at pci0 dev 7 function 4
pchb1: VIA Technologies VT82C686A SMBus Controller (rev. 0x40)
auvia0 at pci0 dev 7 function 5: VIA VT82C686A AC'97 Audio (rev 0x50)
auvia0: interrupting at irq 10
auvia0: ICEnsemble ICE1232/VT1611A codec; headphone, 18 bit DAC, 18 bit ADC, KS Waves 3D
auvia0: variable rate audio
audio0 at auvia0: full duplex, mmap, independent
rtk0 at pci0 dev 20 function 0: RealTek 8139 10/100BaseTX
rtk0: interrupting at irq 11
rtk0: Ethernet address 00:50:bf:e9:3b:7d
ukphy0 at rtk0 phy 7: Generic IEEE 802.3u media interface
ukphy0: OUI 0x000000, model 0x0000, rev. 0
ukphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
isa0 at pcib0
com0 at isa0 port 0x3f8-0x3ff irq 4: ns16550a, working fifo
com1 at isa0 port 0x2f8-0x2ff irq 3: ns16550a, working fifo
pckbc0 at isa0 port 0x60-0x64
pckbd0 at pckbc0 (kbd slot)
pckbc0: using irq 1 for kbd slot
wskbd0 at pckbd0: console keyboard, using wsdisplay0
pms0 at pckbc0 (aux slot)
pckbc0: using irq 12 for aux slot
wsmouse0 at pms0 mux 0
lpt0 at isa0 port 0x378-0x37b irq 7
pcppi0 at isa0 port 0x61
midi0 at pcppi0: PC speaker
sysbeep0 at pcppi0
isapnp0 at isa0 port 0x279: ISA Plug 'n Play device support
npx0 at isa0 port 0xf0-0xff: using exception 16
fdc0 at isa0 port 0x3f0-0x3f7 irq 6 drq 2
fd0 at fdc0 drive 0: 1.44MB, 80 cyl, 2 head, 18 sec
isapnp0: no ISA Plug 'n Play devices found
Kernelized RAIDframe activated
wd1: no disk label
wd1: no disk label
boot device: wd0
root on wd0a dumps on wd0b
root file system type: ffs
wsdisplay0: screen 1 added (80x25, vt100 emulation)
wsdisplay0: screen 2 added (80x25, vt100 emulation)
wsdisplay0: screen 3 added (80x25, vt100 emulation)
wsdisplay0: screen 4 added (80x25, vt100 emulation)
cd0(pciide0:1:0):  Check Condition on CDB: 0x43 00 00 00 00 00 00 00 0c 40
    SENSE KEY:  Illegal Request
 COMMAND INFO:  115014 (0x1c146)
     ASC/ASCQ:  Illegal Field in CDB

cd0(pciide0:1:0):  Check Condition on CDB: 0x28 00 00 00 00 00 00 00 01 00
    SENSE KEY:  Illegal Request
 COMMAND INFO:  115016 (0x1c148)
     ASC/ASCQ:  ASC 0x64 ASCQ 0x09

cd0: dos partition I/O error
cd0(pciide0:1:0):  Check Condition on CDB: 0x43 00 00 00 00 00 00 00 0c 40
    SENSE KEY:  Illegal Request
 COMMAND INFO:  115023 (0x1c14f)
     ASC/ASCQ:  Illegal Field in CDB

pciide0:1:0: lost interrupt
	type: atapi tc_bcount: 60 tc_skip: 0
pciide0:1:0: bus-master DMA error: missing interrupt, status=0x20
pciide0:1:0: device timeout, c_bcount=60, c_skip=0
cd0: transfer error, downgrading to PIO mode 3
cd0(pciide0:1:0): using PIO mode 3
pciide0:1:0: lost interrupt
	type: atapi tc_bcount: 28 tc_skip: 0
IP Filter: v3.4.29 initialized.  Default = pass all, Logging = enabled
IP Filter: v3.4.29 unloaded

(end of dmesg output)

Kindest regards,

Tom