Retro Computer

Hi All,
inspired by discussion in the Electronics Wednesday group I have decided to build a retro computer based on the 6502 chip. A couple of weeks back I received a backplane from I’ve completed the assembly and it’s ready to go.


Yesterday I got my PCB’s back from China and have started building the single step/debug board.

The PLCC socket is for a Xilinx CPLD. I’ve reduced the debug circuitry from 6 or so 9 74’ series TTL chips to a single device.


The schematic below is taken from the 6502 Hardware Manual. It’s the circuit suggested by MOS for debug/single stepping. The functions shown, things like button debounce and RDY signal control have been translated into Verilog and compiled into the CPLD. I will upload the sample code to the MHV GitHub account when I get a chance.


Had a busy day yesterday and managed to complete the last of the 4 board designs I’ve been working on, the processor board.

I sent it to JLCPCB, a big outfit in China. Ordered 5 of each board, 20 in total. Two designs are 75x100mm, two are 100x100mm. The total charge, including DHL 3 day delivery was AUD50.

24 hours after the order was placed the boards are being silkscreened. If you have 30 mins free then It’s likely the same factory processing my order.

With any luck they’ll be delivered before next weekend.


The logistics gods have smiled and DHL delivered my boards this afternoon. Now if they can do the same for Toll and my Element14 order I just may have something fun to do over easter.