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SBC6120 PDP-8 Replica

PostPosted: Sun Nov 25, 2012 8:23 pm
by TRS80
Very little time on retrocomputing over the last couple of months between work and the farm but have finally completed the main board for the SBC6120 PDP8 replica.

The challenge was not building the board (definitely not a beginner project but easy if you are competent at soldering) but getting the required parts. The kit that I got from the US was a partial kit so only included the HD6120 (the Harris PDP8 on a chip), programmable parts (GALs, ROMs) and RAM.

That still left a long list of other parts required and unfortunately I couldn't find a local supplier that could get everything. One of the challenges of a kit produced in 2003 (who would have thought that 2003 was old) is that parts may no longer be available. Ended up geting most parts from Mouser in the US and the HD6402 UART and the oscillator modules from Shenzen, China via eBay. What really surprised me was the cost of mechanical parts like the reset switch.... to get the part that matches the circuit board was NZ$15. The actual chips are cheap by comparison.


The date code on the HD6120 (PDP-8) is 1983 so almost 30 years old and the HD6402 (UART) is 1991.

It works well. Boots OS/8 from the compact flash card and runs all the important PDP8 software like Startrek and Hunt the Wumpus!

Hope to get some time to work on the front panel over the Xmas period and then back to the PDP11.