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RX01/RX02 disk archive and restore programs

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Martin Eberhard

Sep 8, 2023, 5:02:21 PM9/8/23

I've written a couple of PDP8 programs to transfer RX01 and RX02 full-disk images (such as the .RX01 and .RX02 files in David Gesswein's collection) to and from floppy, via a serial port. These programs do more or less what dumprest does, with the following differences:
1) They do not require a special program on the PC side, because the file transfer uses the Xmodem protocol. Teraterm, for example, works perfectly.
2) They are a lot more verbose, both for normal use, and for debugging disk and com errors.
3) They are pretty quick, because they transfer serial port data a track at a time, so that they can interleave disk accesses for max speed.
4) MAKEDISK verifies what it writes by reading each track back after it is written.
5) For single-density disks, only one memory field is required, and the standard RIM and BIN loaders are preserved in that field. (Double density disks require a 2nd field, still preserving the loaders.)
6) Both programs can run in any memory field.

As an example, with the serial port set at 38.4K baud, writing and verifying a complete single-density disk takes less than three minutes.

I've tested these programs with the following configurations:
1) RX02 drive, single-density disk
2) RX02 drive, double-density disk
3) RX02 drive emulating an RX01 (internal switch setting)
All of the above using a single serial port - both for dialog with the user and for Xmodem data transfer)
All of the above, with two serial ports - one for user dialog, the other for transferring Xmodem data

Both programs are heavily (excessively) commented. Complete instructions for their use and customization are at the beginning of each program.

I assemble PDP8 code using PALBART, so I expect these to assemble correctly with PAL-8 too.

You can find MAKEDISK here:

You can find SAVEDISK here:

Martin E.

Dave McGuire

Sep 8, 2023, 6:09:24 PM9/8/23
On 9/8/23 17:02, Martin Eberhard wrote:

Oh, very nice work! We'll definitely use of these at LSSM. Thank
you for doing this.


Dave McGuire, President/Curator
Large Scale Systems Museum
New Kensington, PA

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