>Megan wrote:
> >So when under the command in RT-11:
> >FORMAT DY0:/SINGLE
> >all that happens is that the density bit in the sector header is set
> >to "Single Density", but a complete LLF (Low Level Format)
> >is not done, in fact can't be done, using a DEC RX02 drive.
> >Likewise, the RT-11 command:
> >FORMAT DY0:/DOUBLE (the default)
> >sets the density bit in the sector header to "Double Density"
> >and again can't be done with a DEC RX02 unless the floppy
> >media is already LLF.
> If you have a DSD disk unit with a floppy, that will truly
> format the floppy. The only disk drive/system from DEC
> which could format a floppy is the PDT-11/150 (!)
Jerome Fine replies:
I have an DSD unit with a floppy (DSD 880/30) and have
performed an LLF on an RX02 media.
But I did not know that the PDT-11/150 was also able to
do an LLF as well. Thank you!
However, does the PDT-11/150 use an actual DEC RX01
floppy drive or something a bit different? With the answer
to this question, it should be possible to determine if the
RX01 has some of the smarts to do an LLF, but when
connected to a Qbus RX01 controller, the combination
is not capable - OR DEC did not make public the command
codes to cause the RX01 drive to do an LLF?
> This was discussed at some length on a DEC-interal mailing
> list following the sale of PDTs to employees. It turns out
> that the PDT writes all the formatting info for any track it
> writes, so if you write to the entire disk, it will be
> formatted single density.
Please confirm that the PDT-11/150 uses ONLY RX01 media.
ALSO, is the device driver for the PDT-11/150 the PD.SYS
file? I seem to remember that the PDT-11/150 did NOT have
a hard drive, is that true? If the PDT-11/150 does have a
hard drive, which hard drive and what is the name of the file
for the device driver?
> You can then take the disk to another drive (RX02) and change
> the density to double.
That was the essence of my reply above with the two different
commands under RT-11 using a DEC RX02 floppy drive.
What would be helpful is is you would confirm (or deny - since
I am always making mistakes) that the FORMAT command
under RT-11 for 8" floppy media on a Qbus/Unibus system
ONLY sets the density bit in the sector header of the media.
BUT, before that can be done, a successful LLF must occur
with that media.
The DSD 3rd party floppy drives were one method.
You have confirmed that a PDT-11/150 is a second method.
> At one point when I had an office on ML5-5 at DEC, I had a
> floppy which was held to a filing cabinet by a large disk
> magnet. When people wanted proof, I would take it down and
> demonstrate it as being unreadable, then would format it in
> a PDT-11/150 I had, and then proceed to use it...
While I have no doubt that the PDT-11/150 can do an LLF
on an 8" floppy media and your demonstration was evidence
of that fact, I do not agree that it was proof. I have, on many
occasions, had an 8" floppy which I could not read on a
DEC RX02. It had already had an LLF, but all attempts
to read the media were unsuccessful or unreadable. On a
Qbus PDP-11/23 with a DEC RX02 drive, I used the
RT-11 command:
FORMAT DY0:
and it was successful and I could again read the 8" media.
So while the magnet would likely do a bulk erase, it is not
proof that it was done and that an LLF was required - yes
99.9% of the time I would agree it would be necessary, but
very rarely it might not.
> >The same situation occurred with the DEC RX50 floppy media.
> >The DEC RX50 drive could NOT perform an LLF.
> There was, however, a ROM which was available (at least I had
> one at one point) which allowed formatting of RX50 media on
> a PRO series machine...
You mentioned that a few years ago. Did the LLF process
use the RT-11 command or was XXDP used? Since I
can't remember if XXDP ran on a PRO350, I am curious.
Also, I just remembered that a Rainbow could also do an LLF
on an RX50?????????????
Sincerely yours,
Jerome Fine
--
If you attempted to send a reply and the original e-mail
address has been discontinued due a high volume of junk
e-mail, then the semi-permanent e-mail address can be
obtained by replacing the four characters preceding the
'at' with the four digits of the current year.
Received on Fri May 30 2003 - 16:17:01 BST