Re: SCSI tape problem, 2.1.88

Richard B. Johnson (
Fri, 15 May 1998 16:27:04 -0400 (EDT)

On 15 May 1998, Pat Huber wrote:

> I have a dual PII (300) system on an ASUS P2L97-DS mainboard. The
> system boots from an ATA drive on the EIDE interface and has a
> built in AH2940UW SCSI interface which controls an external disk
> and external DLT in seperate boxes. The devices are as follows:
> Vendor: QUANTUM Model: DLT7000 Rev: 1B41 (tape)
> Vendor: QUANTUM Model: QM318000TD-SW Rev: N1B0 (disk)
> Total cable length is 60", well within spec.
> When I try to tar from the disk to tape (%tar -cvf /dev/st0 bigdisk)
> I get (after about 100 megs of data transfer):
> kernel: scsi0: CMDCMPLT without command for SCB 3, QOUTCNT 0,
> QINCNT 0, SCB flags 0x0, cmd 0x0
> However, tarring from the ATA disks works just fine. This leads me
> to believe that there is an interrupt problem when running two devices
> on the AH2940UW. Is this right? Is there a fix. Note that I am using
> (not by choice) RH4.2.
When it comes to interrupts, N devices on the SCSI bus doesn't mean
anything. It looks like the usual termination problem to me.
Check that the external terminator at the end of the line really has
power. There is a fuse on this board that will blow if a SCSI ribbon
connector is accidentally plugged in backwards. You can enable TRMPWR
on all the SCSI devices (they have isolation diodes). This will make
sure that there is always power on the bus to feed the terminators
even if the controller board fuse is blown. Note that you need terminators
on both ends of the bus and none at the middle (your controller).

Dick Johnson
Penguin : Linux version 2.1.101 on an i586 machine (66.15 BogoMips).
Warning : It's hard to remain at the trailing edge of technology.

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