On May 30, 9:08, Jerome H. Fine wrote:
>Jochen Kunz wrote:
> > > On 2003.05.29 20:27 Jerome H. Fine wrote:
> > > John, if you are reading this, it would be best if you could
> > > confirm - also even better if you could explain why they
> > > hardware to read the DEC RX02 8" floppy media is
> > > not available on a PC.
> >
> > I am not John, but this may be the explanation:
> > The RX02 uses double density only for the data inside the sector.
The
> > sector header is (mostly) the same as a RX01 sector header and it
is
> > rcorded in single density.
> NOTE that most 3rd party RX01/RX02 controller/drive pairs
> for DEC PDP-11 hardware were able to do the complete
> LLF for RX01/RX02 media. In fact, I seem to remember that
> the controller was not required - the drive contained the ability
> to do a LLF off-line. This was not the RT-11 FORMAT
> command, but a complete LLF.
No, that's backwards. In the case of DEC RX01 or RX02 with a DEC
controller, the controller card (in the QBus or Unibus) is fairly dumb,
it's just an interface. The "smart" stuff is in the drive enclosure.
The controller passes a FORMAT command to the drive, the drive
chunters away and executs it, and reports back to the controller when
it's done.
In the case of third-party controllers with "industry standard" drives,
the controller is "smart" and the drive is dumb. The controller does
the formatting, and sends control signals and a data/clock bitstream to
the drive, so you can't do anything
> The same situation occurred with the DEC RX50 floppy media.
> The DEC RX50 drive could NOT perform an LLF.
It works differently than an RX01/RX02. In fact it works exactly like
the third-party RX01/RX02 case above, except that DEC saw fit not to
include formatting routines in the RQDX1/RQDX2 controller. The RX50
drive is an oddly-engineered variant of an industry-standard 5.25" dual
floppy, with almost exactly the same control/data signals.
> However, by the time that DEC allowed the RX33 on the RQDX3,
> DEC had switched to industry standard HD PC 1.2 MByte floppy
> drives and media with 2400 blocks.
Yes, the RQDX3 includes firmware that can do the formatting. However
the layout it creates is fixed, and not useful for an RX50 (which has
almost exactly the same hardware interface as an RX33).
> The question that is still unanswered is IF the board that dbit
> has available that supports the RX01 floppy media on a PC
> with the appropriate 8" floppy drive CAN ALSO support
> an RX02 media? I seem to remember that the answer is NO!
Correct. The answer is "no", for exactly the reason Jochen describes,
and indeed John's webpage says so.
--
Pete Peter Turnbull
Network Manager
University of York
Received on Fri May 30 2003 - 13:10:00 BST