Ethan's Retrocomputing Corner - SBC6120

I got my first PDP-8 in 1982 - a PDP-8/L from the Dayton Hamvention for $35 and a couple of swap items. Twenty years later, when Bob Armstrong made SBC-6120 boards available for under $100, there was no question - of course I had to build one. I'm also in the process of building an IOB6120 to give it some extra I/O capabilities (including an entire VT52 embedded in the FPGA), and an FP6120 for lights and switches (pictures of those to follow)


The bare SBC6120, as mounted in an Amiga external 3.5" disk enclosure. It's almost entirely unmodified (I did have to remove some plastic from the bottom that formerly supported the disk mechanism). Note the convenient square hole at the back of the enclosure - normally, that's filled with a DB-19 for daisy-chaining the drives together. It's at the perfect spot for viewing the status LEDs and accessing the reset button.

SBC-6120 with the RAMdisk (closeup shows details of the odd hybrid SRAMs I found in a junk drawer - four smaller SRAMs on a ceramic carrier with a logic IC embedded in the middle for chip select).

SBC-6120 with a CompactFlash adapter mounted on a simple perf-board carrier. This particular CF module is "8MB" (8,000,000 bytes, really), so there's only room for two partitions, but that's enough to play around.

The two small holes in the perf board over the serial jack were going to be for an RJ-45 connector. My intention was to rig up an internal serial connector compatible with Cisco's RS-232 plugs, but it was quicker to externally mount a PC serial dongle and pass the cable through the former disk drive cable hole.


Spare Time Gizmos
Bob Armstrong's site for the SBC-6120

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