Quantum LTO-2 tape drive and 29160N: bad wide negotiation

My system is NetBSD/i386 4.0_BETA from around May 1.

I have been using a DDS3 on a 2940A for a very long time with absolutely
no problems (well, other than occasional media errors and that the tapes
are too small).

I have a shiny new Quantum LTO-2 tape drive, with a wide connector
(68-pin micro).  I got an Adaptec 29160N "Ultra 160" controller, with an
external 50-pin micro connector, because the 29160 was 64-bit PCI and
not listed as supported in NetBSD.

I have a 50-pin to 68-pin cable connecting the controller to the tape
drive.  For reasons I don't understand the controller negotiates 16-bit
transfers with the tape drive.

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

st0 at scsibus1 target 5 lun 0: <CERTANCE, ULTRIUM 2, 1914> tape removable
st0: drive empty
st0: sync (50.00ns offset 127), 16-bit (40.000MB/s) transfers
ahc2:parity error detected in Data-in phase. SEQADDR(0x1ae) SCSIRATE(0x95)
ahc2:parity error detected in Data-in phase. SEQADDR(0x1ae) SCSIRATE(0x95)
ahc2:parity error detected in Data-in phase. SEQADDR(0x1ae) SCSIRATE(0x95)
ahc2:parity error detected in Data-in phase. SEQADDR(0x1ae) SCSIRATE(0x95)
ahc2:parity error detected in Data-in phase. SEQADDR(0x1ae) SCSIRATE(0x95)
ahc2:parity error detected in Data-in phase. SEQADDR(0x1ae) SCSIRATE(0x95)


I then hooked up the drive to the old controller, and it seems to work,
but it stops/starts which isn't good.  I don't understand why this isn't
going for 20 MB/s transfers.

ahc1 at pci1 dev 1 function 0: Adaptec 2940A Ultra SCSI adapter
ahc1: interrupting at ioapic0 pin 22 (irq 10)
ahc1: aic7860: Ultra Single Channel A, SCSI Id=7, 3/253 SCBs
scsibus0 at ahc1: 8 targets, 8 luns per target

st0 at scsibus0 target 5 lun 0: <CERTANCE, ULTRIUM 2, 1914> tape removable
st0: drive empty
st0: sync (100.00ns offset 15), 8-bit (10.000MB/s) transfers
st0 detached

I have 2940U2W lying around and may try that.

I will try the SCSI bios to try to set things to the right rates.  Does
anyone have any clues?  Does anyone know if the 29160 (no N) works?

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