Subject: Re: floppy drive conversion
From: Roger Ivie <>
List: port-vax
Date: 06/26/1998 10:10:53
David Hamilton said:
> I have access to a bunch of IBM floppy drives, and I'd like to use one of
> them on my VS2000.

If you just move the drive select over to DS2, it should work well enough
for RX33 diskettes. However, the drives DEC uses change speed based on
the Reduced Write Current input, so you won't be able to read RX50s. 

RX50s are also a problem for the SCSI floppy controller. The floppies are
typically written with a software interleave. The RQDX3 is foolish enough
to de-interleave the floppies for a host, so VMS expects RX50s to be
automagically de-interleaved. At the time the firmware was written, the RX50
question was pushed off; DEC needed to decide whether the controller or the
operating system would de-interleave RX50s. Since DEC never officially sold
the product as an RX33 controller, a decision was never made. Consequently,
the SCSI floppy controller does not de-interleave RX50s.

Until a large customer came along and demanded a bunch of 5.25" SCSI 
floppies that could interchange data with an RX50 box. DEC decided it would
be cheaper to upgrade the controller firmware than it was to upgrade VMS,
so _some_ models of the SCSI floppy controller _do_ de-interleave RX50s.

Roger Ivie