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Wanted: RT-11 OS as a TU-58 image

Its been a pretty long time since I played with this, and I don't totally trust my recollections anymore. But I seem to recall that I could NOT read a larger disk mounted via a TU58 emulator (aka mine) using DD.sys. The OS checked the block count in the driver. So I did some disassembly etc and determined that one could change that behavior by patching "the number of device blocks at octal offset 054 in the driver" with an appropriate value. All I did for RT11 in the driver available at http://www.willsworks.net/pdp11/tu58-emu.htm#RSPDRV
was to patch the existing dd.sys and rename it.
I could be wrong or it may depend on the RT11 version being run. If I get one of my
PDP-11s booted again this summer I will check it out.

I think you could plug in the max tu58 block count for a 'generic' driver and you'd just get a read error if you attempted to read past the end of file. I was perfectly happy with RL02 emulation as its the largest physical disk I owned at the time. Please do note the comment at the bottom of my page above. If you really want to have access to large storage capacity, start playing with more than two TU58 units in addition, I'm told the protocol will support 256!
 
I'm curious about using more than two units in emulation, too. I may experiment with that sometime. I'm thinking of making a standalone TU58 emulator with a different form factor and user interface than the other ones I've seen. I definitely plan to support large volumes up to 65535 blocks, and I may also support multiple partitions accessed by nonstandard unit numbers if I can find a clean way to do that. It helps that the available RT-11 5.3 distribution includes macro assembler source code for the device handlers.
 
NF6X said:
I'm curious about using more than two units in emulation, too. I may experiment with that sometime. I'm thinking of making a standalone TU58 emulator with a different form factor and user interface than the other ones I've seen. I definitely plan to support large volumes up to 65535 blocks, and I may also support multiple partitions accessed by nonstandard unit numbers if I can find a clean way to do that. It helps that the available RT-11 5.3 distribution includes macro assembler source code for the device handlers.
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Have you seen this?
 
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