Iomega Zip 100 Problems with "New" ATA

[Crist J. Clark]

I believe that I'm having some problems with a Zip 100 drive and the
"new" (not really so new anymore) ATA driver. I added a Zip and a new
CD-R device to a system over the weekend. The BIOS identifies all of
the new devices just fine, but when I boot FreeBSD (the only OS on the
system), I get to the ATA probes and things lockup (these are from
notes, not exact),

  ad2: READ command timeout tag=0 serv=0 - resetting
  ata1: reseting devices... done
  ad2: <IOMEGA  ZIP100> (blah, blah) PIO0

And it just hangs there forever, no Ctl-Alt-Del, no nuthin', hit the
reset button on the case.

The Zip is the slave on the secondary controller. I've had the problem
with 4.8-RELEASE and a very recent 4.8-STABLE. I've tested with
GENERIC just to make sure it wasn't my kernel config.

I believe this is a problem with the ATA driver and the Zip:

 1) If I pull the power on the Zip (still in the case, still on the
    ribbon), everything boots up fine.

 2) If I boot up a 4.5-STABLE-p1 kernel on the HDD, all devices are
    detected, and we come up in multi-user mode. (Albeit with
    unrelated errors due to a 4.5 kernel and 4.8 userland.)

 3) If I boot off of a 4.5-RELEASE CDROM and put on the 4.5 live FS,
    all devices are detected. This shows the new CD-R probably is not
    the flaky one.

I knew there have been some problems with the new (post 4.5) ATA
code. I've reviewed what I could find in the -stable archives and
didn't find anything specific to Zip drives. Has anyone else seen
problems with Zip drives? Any ways to work around this? Perhaps some
boot vars?