I have the following problem with an Archive Python 4mm drive attached 
to a Adaptec 2940W host adapter: 

When the adapter bios is configured with disconnect enabled, a 'mt 
status' to the tape drive  will hang for a couple of minutes before 
returning with all status fields set to zero. I/O to the disk drives 
on the same adapter is very slow. 

When the bios for disconnects is disabled, I can read and write the 
drive, with the expected side effects on other scsi traffic (ie. long 
delays while the tape is unloading or rewinding).

Anyone seen something like this? 

The NetBSD source is -current as of August 14:

NetBSD 1.2G (SOLSWEB) #2: Thu Aug 21 15:57:35 EDT 1997
    root2@solsweb:/local/src/NetBSD-current/src/sys/arch/i386/compile/SOLSWEB
cpu0: family 5 model 2 step c
cpu0: Intel Pentium (P54C) (586-class)
real mem  = 66715648
avail mem = 60571648
using 840 buffers containing 3440640 bytes of memory
mainbus0 (root)
pci0 at mainbus0 bus 0: configuration mode 1
pchb0 at pci0 dev 0 function 0
pchb0: Intel 82439 (Triton II) TXC Host Bridge (rev. 0x03)
pcib0 at pci0 dev 7 function 0
pcib0: Intel 82371SB (Triton II) PCI-ISA Bridge (rev. 0x01)
Intel 82371SB (Triton II) IDE controller (IDE mass storage, interface 0x80) at pci0 dev 7 function 1 not configured
ATI Technologies Mach64 GX (VGA display, revision 0x01) at pci0 dev 10 function 0 not configured
ahc0 at pci0 dev 11 function 0
ahc0: interrupting at irq 11
ahc0: aic7880 Wide Channel, SCSI Id=15, 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: <WDIGTL, ENTERPRISE, 1.80> SCSI2 0/direct fixed
sd0: 4157MB, 5720 cyl, 8 head, 186 sec, 512 bytes/sect x 8515173 sectors
ahc0: target 1 using 16Bit transfers
ahc0: target 1 synchronous at 20.0MHz, offset = 0x8
sd1 at scsibus0 targ 1 lun 0: <WDIGTL, ENTERPRISE, 1.80> SCSI2 0/direct fixed
sd1: 4157MB, 5720 cyl, 8 head, 186 sec, 512 bytes/sect x 8515173 sectors
ahc0: target 2 synchronous at 6.67MHz, offset = 0xf
st0 at scsibus0 targ 2 lun 0: <ARCHIVE, Python 02779-XXX, 6280> SCSI2 1/sequential removable
st0: density code 0x13, 512-byte blocks, write-protected
ep0 at isa0 port 0x220-0x22f irq 5: 3Com 3C509 Ethernet
ep0: MAC address 00:60:97:9f:43:78
ep0: 8KB byte-wide FIFO, 5:3 Rx:Tx split, utp (default utp)
ep1 at isa0 port 0x300-0x30f irq 10: 3Com 3C509 Ethernet
ep1: MAC address 00:60:97:9e:ea:9d
ep1: 8KB byte-wide FIFO, 5:3 Rx:Tx split, utp (default utp)
ep2 at isa0 port 0x320-0x32f irq 3: 3Com 3C509 Ethernet
ep2: MAC address 00:60:97:9f:40:96
ep2: 8KB byte-wide FIFO, 5:3 Rx:Tx split, utp (default utp)
com0 at isa0 port 0x3f8-0x3ff irq 4: ns16550a, working fifo
npx0 at isa0 port 0xf0-0xff: using exception 16
vt0 at isa0 port 0x60-0x6f irq 1
vt0: generic, 80 col, color, 8 scr, mf2-kbd, [R3.32]
fdc0 at isa0 port 0x3f0-0x3f7 irq 6 drq 2
fd0 at fdc0 drive 0: 1.44MB 80 cyl, 2 head, 18 sec
biomask 840 netmask c68 ttymask c6a
boot device: sd0
root on sd0a dumps on sd0b
root file system type: ffs


-- 
Andreas Wrede              Planix, Inc.
andreas@planix.com         Networking, System Administration, Consulting
http://www.planix.com      Toronto, Ontario, Canada