Retro Computing – Final Touches for TMS9995 on RC2014


It turned out that my TMS9995 system had no modules in common with my CP/M system, as it’s using the ROM and RAM modules left over from the CP/M upgrade. All I needed was another backplane to be able to run both at once.

SC116 3 slot backplane

As the TMS9995 uses three modules: CPU, ROM and RAM I wanted a 3 slot backplane[1], and it turns out that Steve Cousins makes just the thing with his SC116, which is available on Tindie. I ordered one yesterday, and it arrived today :)

It only took a few minutes to put together (in part because I left out all the bits I didn’t need).

Pi terminal server

It’s great to use my RC2014s from a serial terminal on my laptop or PC, but that means I can’t do anything with them when I’m away from home.

To get over that I’ve used the Raspberry Pi that’s sat on the UPS on my desk (my first original Model B) along with a couple of UART cables.

I wanted to get another FT232 cable, but the eBay supplier I used last time is away. So instead I order a pair of PL2303 based cables from Amazon. These turned out to work fine with my laptop, but not so great with the Pi, where I could only get one working at once (due to power issues?), and also hit a somewhat well documented issue with (clone?) PL2303X chips where it’s necessary to sudo modprobe -r pl2303 && sudo modprobe pl2303The compromise I ended up with was the FT232 for the CP/M system using screen -S Z80 /dev/ttyUSB0 115200 and the PL2303 for the TMS9995 using sudo minicom -D /dev/ttyUSB1This means I can now SSH to my Pi and connect from there to the two RC2014 systems.


[1] At some stage I may make a TMS9901 I/O module, and I’d also like to see if I can add a TMS9918 video adapter (like this one), so I might have to upgrade to 5 slots later on.

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