r/PDP11

This moved quickly - I don't have a larger Sipeed board yet, so I dug out an old Zynq 7000 CPU+FPGA board from the cupboard. Bought it years ago but never find the app that would suit it. *until now*

I have it booting RT-11 from an SD card dedicated to the PDP, hardware serial console and 4MB RAM. I am currently adding 3 other serial ports to the Linux fabric with a tu58 emulator on serial1

Next: Move SD card to an RL02 bridge inside linux. My homage to blinken lights on a 8x8 LED grid. After that, its a larger hard drive controller emulation and then ethernet.

https://i.redd.it/uceblsfk7pih1.gif

The 11/34 seems to be working fairly well now. It can successfully boot into RT11XM now. I haven't exercised XM specific functions yet. The 11/35, 40 simulation needs a stack limit register for some of the diagnostics to complete.

For fun, I used simh to create a RK07 RSTS v9.3 disk and tried to boot it. Init would run, but it would halt when starting timesharing. I think that the problem is that the RK611 simulation is missing something - not sure what just yet.

There is also a Programmed Interrupt Request register that seems to be a poorly documented processor register. So far, nothing seems to need it. I have no idea what software uses it.

So things to do, in whatever order strikes my fancy:

• Update RK611 controller
• Implement DZ11
• FIS
• FPP
• 22 bit addressing
• Separate I/D space
• Supervisor mode

I've also implemented an "options" interface for the CPU simulations. For most of them, it does nothing, but for the PDP11, it allows things like enable/disable EIS and other instruction groups, various options of memory management, and other things that seem useful, like setting the switch register value.