30 May
2003
30 May
'03
7:18 a.m.
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 (!)
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.
You can then take the disk to another drive (RX02) and change
the density to double.
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...
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...
Megan