8" floppy drive for PC, RS/6000, 68k Mac or Alpha

From: Jerome H. Fine <jhfinexgs2_at_compsys.to>
Date: Sun Jan 25 10:20:11 2004

>Doc Shipley wrote:

> I want one. I can use a PCI, ISA, EISA, MCA (PS/2 or RS/6k), NuBus
> or QBus adapter. The main requirement is that hardware + software be
> able to low-level format disks to RX02.

Jerome Fine replies:

To start with, first let me say that I understand too
little about hardware issues to be of much help.

As for the 8" RX02 floppy format, remember that
only the data is Double Density, the header is
still Single Density. Also, as far as I know, ONLY
DEC systems used and could handle the SSDD
(Single Sided Double Density) RX02 format.

I am not aware of any other computers and operating
systems that used the RX02, except if you consider
the 3rd party manufactures of DEC compatible hardware.

In that regard, DSD (Data Systems Design) was one of
the companies which sold a number of RX02 compatible
systems, including the DSD 880/30 which had both
an 8" hard drive that emulated 3 * RL02 (but in this
case non-removable) drives and a single RX02 drive
as opposed the the usual dual RX02 drives from DEC.

I still have a couple of DSD 880/30 systems that might
still work. On occasion when I need to read an 8" floppy,
I use them. One aspect of the DSD 880/30 is that the
hardware is also RX03 compatible, although DEC never
actually sold an RX03 floppy drive. BUT, if there were
some 8" drives, if my failing memory serves me correctly,
which could be attached to an M8029 DEC Qbus board
(the company that made plotters) that would allow both
sides of the 8" floppy to be read.

The definition of an RX03 was DSDD (Double Sided
Double Density), as far as I know. In any case, the
DSD 880/30 has the hardware to use both sides of an
8" floppy, although like the DEC M8029 controller, the
controller for the DSD 880/30 is also limited to just
18 bit addresses for transfers to/from the DMA Silo
or a range of 256 KBytes of lower memory.

Formatting an RX02 could be done in one step using
the DSD 880/30 OFF-LINE to format the floppy
as SSDD. In addition, if an 8" floppy was already
formatted as SSSD, then RT-11 was able to send
a command to the header to make that 8" floppy
able to accept SSDD data. Thus the RT-11 command:
did not actually do a complete LLF format, it was only
able to change an 8" floppy with an already existing
SSSD LLF to a SSDD LLF, i.e. change the header
flag from Single to Double Density.

The DEC RX02 drive was unable to do any LLF at all.
It was able to accept the command under RT-11:

I did manage, by the way, to add a DPDT switch to the
floppy drive in the DSD 880/30 which reversed the
sensors used to detect a Single Sided floppy as opposed
to a Double Sided Floppy. That allowed me to use ALL
SSDD RX02 floppy media as DSDD floppy media
without having to punch the extra holes. In my experience,
the ONLY floppy media I ever found a problem with
were 8" floppies from DEC distributions of software.
Some one had used software distribution floppies from
DEC and I thought it would be worth while to try them.
About 20% did not work as DSDD. Not all blocks
were bad, but a few in some cases.

> And, most importantly, that drive *will* format a disk as IBM 3740
> format, right?

As far as I know, the IBM 3740 format was SSSD or equivalent
to the DEC RX01, or more to the point the other way around.

> I have 3 computers with RX02 drives, about 300 bulk-erased floppies,
> and no way to make the floppies useful in those drives*, and that's
> starting to p_ss me off.

You need either a DSD 440 or a DSD 880 or any of the
other 8" compatible 3rd party systems. The DEC RX01 / RX02
hardware could NOT do an LLF.

> * a couple of places I can trade degaussed disks for formatted at
> varying ratios, and that's probably the cheapest way to go, but that's
> hardly the point, right?

YES!! But remember that a DSD 440 and a DSD 880 is
rather heavy. If an LLF is a one time requirement, then it
would be less expensive to ship a few floppies around.

If you can find someone near by with a DSD system, that
would be best.

By the way, V4.00 of RT-11 did have incorrect code to
handle the Double Density option for an RX03, but
in V5.00, that code was removed. I did manage to
modify DY.MAC for V5.03 of RT-11 to use a DSDD
RX03 floppy PLUS use a bounce buffer in low memory
so that all 4 MBytes of memory under V5.00 of RT-11
could be used by DYX.SYS for the user buffer. I
have mentioned this last part many times, but by now
too few people have a DSD 880/30 system around,
let alone use it with V5.00 of RT-11 and later.

Sincerely yours,

Jerome Fine
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Received on Sun Jan 25 2004 - 10:20:11 GMT

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