8" floppy project

From: Doc Shipley <doc_at_mdrconsult.com>
Date: Tue Jul 27 23:31:38 2004

Ethan Dicks wrote:

> On Tue, Jul 27, 2004 at 10:46:49PM -0500, Doc Shipley wrote:
>
>> Bottom line requirement is that I be able to low-level format an 8"
>>floppy to RX02 format. IIRC, RT-11 can flip the switch from RX01 to
>>RX02 in an RX02 drive, right?
>
>
> Yes. So can OS/8. The "flip" is when an RX02 drive re-writes part of
> the sector to double density. That's what makes them so hard to read
> on non-DEC hardware - the media becomes both single and double density.
>
> Both RX01 and RX02 disks start off with "Industry Standard" IBM-compatible
> low-level formatting, AFAIK. There are third-party DEC-compatible drives
> that can take an absolutely blank disk and lay down tracks. I would think
> a suitable CP/M system could do the same. Post-1982 hardware is where
> things start to get tricky.

   OK. I've heard yea and nay on this count.

   You're saying that on an RT-11 system (no OS/8 or its hardware to
play with), I can take an "IBM 3740 Compatible" SSSD disk out of the
box, run FORMAT/DOUBLE, and have an RX02 diskette? That would help
quite a lot.

> In terms of development and set-up time, I would think a PDP-11 would
> be the fastest way to just dup floppies.

   Yep. Getting blanks to dup *to* is still the issue.

>> I'd *like* to be able to take a disk image of a floppy as a file, and
>>to write that back out to floppy, but that's gravy.

> That's trivial with a VAX (BACKUP/PHYSICAL). There must be a way with
> smaller hardware (2BSD on a PDP-11, perhaps?)

   Hmm. I need to see if I have a Qbus RXV21 that can run in a 22-bit
system. Does VMS/VAX support RX02?

   Or, yes, there's an RX211 driver in 2.11BSD. Problem is getting it
*on* the Unibus box. There have been "issues". And there's still no
way to LL format the target disk.

> I wonder what it would take to hook a real RX02 up to modern hardware. The
> interface isn't complicated, but AFAIK, it would take more than a PeeCee
> parallel port to drive it. Similar to hooking up a real Commodore 1541
> to a modern machine and siphoning off a physical backup...

   Well, there's an interface to make the PC look like an RX02....


        Doc
Received on Tue Jul 27 2004 - 23:31:38 BST