Copying DEC VAX set up disks rx50, help

Dave Dunfield dave06a at
Sun Mar 4 06:06:08 CST 2007

> > Hmm...  Others on the list can chime in with their floppy expertise,
> > but from the way you are describing what you've tried, it doesn't
> > sound as if you have a clear picture of the media in front of you.
> I dunno, RX50 format is easy to copy.  Make sure that your 1.2M drive 
> is declared as such in the BIOS setup--if it's confused with a 1.44MB 
> drive, it's not going to work, as 2D operation on a 1.2MB requires a 
> write clock (300KHz) that conforms to a 360 RPM drive.  A 1.44MB 
> drive is 300 RPM--so any attempt to write a 2D format using a 250KHz 
> clock rate is guaranteed to fail--you'll run out track before you run 
> out of data.

This is not an issue with ImageDisk, which doesn't look at the BIOS
settings at all. My main ImageDisk setup has an internal drive 3.5" HD
rive A which is configured as such in the BIOS, and an external cable
for attaching 5.25" DD40/DD80/HD or 8" drives as drive B, and the BIOS
has been told there is no drive B.

This makes it easy to work with ANY drive type - but the downside is
that you may have to set a data-rate translation if you are recreating
the disk on a different drive type than the one from which it was

dave06a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools:
com             Collector of vintage computing equipment:

More information about the cctech mailing list