PDP-11/45 RSTS/E boot problem

Fritz Mueller fritzm at fritzm.org
Tue Feb 5 12:03:14 CST 2019

> Perhaps compile [test programs] under SimH and do a block-level diff of the image with what is currently in use, and transfer just those blocks?

I did experiment with this a little way back.  I wrote a small standalone code that dumps a CRC of every sector over the console; I can run this both under SIMH and on the real machine, then diff to find the changed sectors.

Unfortunately, when I tried to apply this, it seemed that SIMH's write single sector wasn't working correctly for me (though "write all sectors to end" seemed to work okay).  It ended up being much more tedious than I had thought to do it this way; in the end I concluded I'd be better off writing some different software specifically for this purpose, but I haven't gotten back to it yet.

FWIW, I maintain a Windows VM (on a MacOS X host) for the sole purpose of running PDP11GUI, and I use an USA19H USB serial dongle connected through to the VM as a serial interface.  I don't know if something about this setup is particularly detrimental to PDP11GUI transfer performance?  It takes me >3hrs to write a 2.5mb pack this way (at 9600 baud), or a little over 1hr to read one back.  Do others see similar throughput with these tools?


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