microRSX-11 is a expanded subset of RSX-11/M plus and was targetted at the microPDP-11 family of machines. Here is an archive of a distribution set of RX50 floppies I was recently given:

In my missing to archive all software I have for my PDP-11, I’ve spent some time working through my RX50 disks. Here are the results of my labours

I archived them using John Wilsons excellent PUTR utility using a PC fitted with a 5.25″ floppy drive (as drive B:). Here is the process I used:

• Start up PUTR
• Mount the RX50 in foreign mode with:MOUNT B: /FOREIGN /RX50
• Then for each floppy:COPY/DEV/FILE B: [imagename]

Here are the initial set of disk images I have created. I’ve not had a chance to look at them in detail, but there looks like there is plenty of stuff that is of interested to the general community:

One of my main fears with my collection is loosing software over time as disks slowly decay. DEC media has proven amazingly resilient with many of my disks well over 30 years old. The reality is though that they won’t last forever and so I’ve decided now is the time to start a program of archiving them all to modern media.

I have the following to work my way through:

• 40 RL02 packs
• 24 RL01 packs
• ~250 RX01 and RX02 floppies
• ~100 RX50s
• 24 TU56 tapes
• ~100 TU58 tapes
• 28 RK05 packs

Software wise, these will yield a mixture of XXDP, RT-11, RSX-11/M, RSX-11/M PLUS, and Unix software. As I complete them I will put any useful finds online to download for others to use.

RT-11 is restricted to each devices is limited to 32MB of usable space. This is due to the filesystem using a 16-bit field to represent blocks, giving a maximum of 65535 x 512 byte blocks.

For larger MSCP disks, such as RD53, RD54, RA series and third party disks, all is not lost. Within RT-11 a mechanism exists to partition the disk into multiple logical drives allowing you to access the remaining disk space.

To achieve this, issue the commands:

SET DU[id] DEVICE=[unit]
SET DU[id] PART=[part]
SET DU[id] PORT=[port]

Where:

• id is the numerical number of the DU devices you wish to map onto your device. This is in the range 0-7 on versions of RT-11 prior to 5.4
• unit is the unit number of the device you wish to map onto the DU device.
• part is the ‘partition’ number within the device you wish to map. So PART-0 would be the first 32MB of the disk, PART=1 would be the next 32MB and so on
• port is the MSCP device number. If you only have a single MSCP controller on you machine this would be PORT=0

So for example, if you have  an RD54 currently on DU0, you could access the remaining space with the commands:

SET DU1 PORT=0
SET DU1 DEVICE=0
SET DU1 PART=1

SET DU2 PORT=0
SET DU2 DEVICE=0
SET DU2 PART=2

SET DU3 PORT=0
SET DU2 DEVICE=0
SET DU2 PART=3

You will now have 4 devices, DU0,1,2,3 each with 32MB of space.

Whilst this is very useful, there is a bit of a sting in the tail in that the DU id range is only 0-7 on all but the most recent versions of RT-11. This limits you to a maximum of 8 32MB devices, which whilst a huge amount of space by PDP-11 standards, still doesn’t allow you to access all of the space on some of the more modern disks.