[pups] booting RT11 from alternate controller

Jonathan Engdahl j.r.engdahl at adelphia.net
Wed Apr 2 13:58:31 AEST 2003

I have a PDP-11/53 with a SCSI controller at 172150, and an RQDX3 at 172144.
There are a couple SCSI drives on the primary controller, and an RX50 on the
RQDX3. Everything seems to work OK, and I can read the floppies, except I
cannot boot RT11 from a floppy. From the 11/53 boot ROM you can say


It will then ask for the address of the alternate controller. It reads from
the floppy, then it reads from both hard drives, then hangs.

What I hunch is happening is that the boot ROM reads the RT11 boot sector
from the floppy, but then the boot sector tries to continue booting from the
hard drives, which isn't going to work, because they are 2.11BSD formatted.

The objective is to have some non-RQDX3 hard drive controller as the
primary, and a secondary RQDX3 for the floppy, and to be able to boot UNIX
from the hard drive, and RT11 from the floopy. Any ideas on how to
accomplish this?

Jonathan Engdahl

"The things which are seen are temporary,
 but the things which are not seen are eternal."  II Cor. 4:18

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