8" drive hooked up to a PC

From: Ethan Dicks <erd_6502_at_yahoo.com>
Date: Fri May 30 08:17:00 2003

--- Jochen Kunz <jkunz_at_unixag-kl.fh-kl.de> 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. Result: A RX01 holds 128 Bytes per sector, a
> RX02 holds 256 bytes per sector, thus doubling the capacity. So the
> floppy controller has to switch the data rate from sector header to
> sector data... A really, uhhm, "interresting" design.

That is, essentially, the case. A DEC drive can take an IBM-formatted
floppy (RX01 format) and scribble the right things on it to make it an
RX02 floppy, but only third-party drives (Data Systems Designs, et al.)
can start with a blank floppy. Unlike "modern" machines, there is no
"floppy chip" in an RX01 or RX02 drive - it's all done with TTL,
PROMs and discrete components. When floppy controller chips became
popular, they didn't spend a lot of time on "oddball" formats.

The data-portion of the RX02 is what a PeeCee FDC can't digest. It
*might* be possible to program an Amiga to digest RX02 disks (it also
lacks a dedicated FDC - it uses a 4096-bit shift register in the sound
chip to import the data, and (for MFM formats) miniterms applied by
the graphics co-processor to translate back and forth to plain binary
data). The Catweasel should be able to handle it, but, as has been
hashed out here before, you'd have to roll your own with it; the software
support is severely lacking compared to the capability of the hardware.

-ethan
Received on Fri May 30 2003 - 08:17:00 BST