NS32CG160 single board computer

The rev. 1.0 boards have been in my hands for a couple of weeks. Except for a bad memory chip (replacing it was a bear), everything tested so far is working. The GAL chips have been tested at 5ns speed, and at 15ns speed. The latter chips are currently in use @25mhz. All of the TTL components on the board are 74LSxx, the exception being the 74ALS646; the ALS version of the chip is a good bit cheaper than the LS version.

The biggest concern was whether the dynamic bus sizing for the ROM chip would work. This was the approach I took on my early NS32016-6 board back when the National Semiconductor line was brand new.

The rev. 2.0 board incorporates the 1.0 errata sheet to correct the wiring error which affects both memory chips. The Bill Of Materials has no chages, and the four PLD's are unchanged. There is no substantial change to the board layout, so the pictures below are not update.

[There is also a companion 4Mb memory board, up to 4 of which may be used as external 16-bit memory. This is the first use of the defined, but never implemented, 16-bit data path on the RetroBrew ECB bus.]

The schematics, board layout docs, PLD ied files, bill of materials, and errata are all combined into a single zip-file which may be downloaded here: ns32cg160_rev_1-0_all_docs.zip

Photo 1. The fully completed board.

Photo 2. The bare board ready to be built up.

Photo 3. The underside of the bare board.

There are 3 LEDs on the board. Colors are important: RED for operation in Supervisor Mode; GREEN for operation in User Mode; and BLUE for the wait or halt condition. Test programs as currently written will either halt in User Mode (green) so signal successful termination, or in Supervisor Mode (red) to signal an error condition. During full speed operation the blue LED does not come on, except for certain instructions which take a long time to execute. I have noticed the blue LED to flicker partially on during a single instruction string operation scanning memory (SKPSD mnemonic). Stand-alone operation uses the Molex power connector, or RetroBrew bus operation using the 96-pin DIN connector.