Reading RX01/02 disks on a PC

From: Jerome H. Fine <>
Date: Sat Feb 5 19:01:11 2005 wrote:

>>I'm assuming since I can't find anything about subdirectories on RT11 that
>>they don't exist?
>Virtual disks (aka logical disks) give most of the functionality of
>subdirectories. RT-11 V5 and later has them built in, for earlier versions
>there are DECUS drivers to give you this functionality.
Jerome Fine replies:

Further to Tim's answer, the device driver is
LD(X).SYS and is currently a data only device.

Essentially, ANY file (usually with the default
extension of DSK) can be MOUNTed as a logical
device, although more than 2 or even 3 levels
within successive logical files are extremely
rare, but not prohibited. The command is:


after which LDn: can be used as any data device
as long as the DEV device driver is resident/loaded.

Starting with V05.06 of RT-11, up to 64 logical
devices can be used, although DEC had plans for
the last 32 logicals and there seems to be a
restriction for novice RT-11 users as far as the
second set of 32 logicals are concerned. For
myself, when I helped set up a V05.06 system,
I "reserved" only the last 8 logicals and used
L70:, L71: and L72: as reserved devices leaving
the other 56 logicals available.

In that environment, it was often useful to be
able to "INSPECT" a logical device without the
MOUNT command. I modified DIR to allow:
DIR DU0:/VOL:nnn
where nnn was the starting block number of foo.DSK
on the DU0: device.

Any other questions?

Sincerely yours,

Jerome Fine
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Received on Sat Feb 05 2005 - 19:01:11 GMT

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