Manuel Bouyer <bouyer@antioche.eu.org> writes:

> Well, you have a 16bit-capable adapter and 16bit-capable target, so they
> negotiate 16 bits. They have to way knowing that the cable is only 8 bits
> (other than the parity error when trying to use the 16-bit path).
>
>> I will try the SCSI bios to try to set things to the right rates.  Does
>
> This may help

It helped a lot (and worked), but the 29160 with wide disabled
negotiated only at 20 MB/s instead of 40 or 80.  I haven't figured out
why.

ahc2 at pci1 dev 2 function 0: Adaptec 29160N Ultra160 SCSI adapter
ahc2: interrupting at ioapic0 pin 18 (irq 5)
ahc2: aic7892: Ultra160 Wide Channel A, SCSI Id=7, 32/253 SCBs
scsibus1 at ahc2: 16 targets, 8 luns per target
scsibus1: waiting 2 seconds for devices to settle...
st1 at scsibus1 target 5 lun 0: <CERTANCE, ULTRIUM 2, 1914> tape removable
st1: drive empty
st1: sync (50.00ns offset 127), 8-bit (20.000MB/s) transfers

>> anyone have any clues?  Does anyone know if the 29160 (no N) works?
>
> Yes, it does.

I will probably order one.  It would be good to edit it into ahc(4).

I had an old 2940U2W, and I tried that, and it works well:

ahc3 at pci1 dev 5 function 0: Adaptec 2940 Ultra2 SCSI adapter
ahc3: interrupting at ioapic0 pin 18 (irq 5)
ahc3: aic7890/91: Ultra2 Wide Channel A, SCSI Id=7, 32/253 SCBs
scsibus2: waiting 2 seconds for devices to settle...
st1 at scsibus2 target 5 lun 0: <CERTANCE, ULTRIUM 2, 1914> tape removable
st1: drive empty
st1: sync (25.00ns offset 127), 16-bit (80.000MB/s) transfers

It's U2, not Ultra160, so it is supposed to max out at 40 MHz bus speed.
I can get about 23 MB/s data with 32k block size.  Larger blocks don't
seem to help.  Amanda wrote at 22837 kb/s average rate for 9G worth of
actual dumps (26 files, some 3.3G, some little).

Thanks for the help.