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Introduction
David Conroy over at http://www.fpgaretrocomputing.org/pdp10x has created a (customized) PDP10-on-FPGA system which he calls the PDP-10/X, and has extensively documented his work on that site. In October 2018, he made an archive of the development environment of this system available to a member of the RetroBrewComputers.org community, who posted that archive here: https://www.retrobrewcomputers.org/forum/index.php?t=msg&th=333
In that thread, there were efforts to use some of Conroy's existing boards and to use newly manufactured boards to create a working system. However, both approaches required soldering a 208-pin 0.5mm pitch TQFP package for the FPGA, which is challenging to say the least.
I noticed that the same FPGA, a Xilinx Spartan 3E, was available as a development board from WaveShare.com, so no SMT soldering required. (They make the same board available on eBay). After checking that enough pins were available on the FPGA board, I set out to create a new system board in KiCad. I eventually got that redesign of the system board to work, and posted my results in that thread.
I decided that since the FPGA is a bit expensive ($35), the board could stand to have more utility than just running Conroy's PDP-10/X, so I added the parts needed to run a Multicomp system to get to the board described here.
Features
- Supports the WaveShare Core3S500E board, which contains a Xilinx Spartan 3E with about 500K logic elements (LE), about 45K on board SRAM, and 116 I/O pins. The board is designed to be pin compatible with other WaveShare FPGA boards, including some of the Altera ones, but I have not used one of those yet.
- 2.5 MB of SRAM (5x 512KB by 8 SRAM chips)
- 4MB of Serial EEPROM, used by the PDP-10/X (could be supported by Multicomp but currently is not).
- TTL 6-pin Serial port (used by both PDP-10/X and Multicomp)
- DS1337 I2C Real Time Clock, with coin-cell battery backup (PDP-10/X support only)
- 40-pin IDE port (PDP-10/X support only, can be used as general GPIO in a Multicomp system)
- WizNet Ethernet support (PDP-10/X only)
- VGA, PS/2 (5V & 3.3V) and SD card interfaces (Multicomp only)
The board uses a standard 5V/2A wall-wart DC power supply with a 5.5mmx2.1mm connector jack.
