Novasaur - Retrocomputer, late-70’s TTL logic, no MPU

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By Alastair Hewitt, and ot entirely unlike the Gigatron, but with lots of RAM and ROM and able to run CP/M (by emulating an 8080). Uses ROM for the ALU function.

The Novasaur is a full-featured personal computer built from less than three dozen Advanced Schottky TTL chips (circa 1979). It supports an 80-column SVGA text display, PS/2 keyboard, programmable sound generator, RS232 serial, and an Intel 8080 byte-code interpreter. The machine is capable of running early 80’s computer games and CP/M using a built-in 254k RAM disk.

  • Dual Processor CPU/GPU (Harvard Architecture).
  • 33 MHz dot clock, 16.5 MHz data path, 8.25 MHz per processor (~3.5 CPU MIPs)
  • 256k ROM: 96k ALU, 64k native program, 64k cold storage, 32k fonts.
  • 512k RAM: 7 banks of 64k user, 60k display, 4k system.
  • 76 ALU functions including multiply/divide, system, and math functions.
  • Bitmapped Graphics: Hi-res mode up to 416x240 with 8 colors and 4 dithering patterns. Lo-res mode up to 208x160 with 256 colors, double buffered.
  • Text Mode: 8 colors FG/BG, 256 line buffer, up to 104x60 using 8x8 glyphs, 80x36 and 64x48 rows using 8x16 glyphs.
  • Audio: 4 voice wavetable synthesis, ADSR, 8-bit DAC, 8Hz-4.8kHz.
  • PS2 Keyboard: Native interface built in.
  • RS232 Serial Port: Full duplex, RTS/CTS flow control, 9600 baud.
  • Expansion Port: 7 addressable 8-bit register ports, 4 interrupt flags
  • Chip Count: 34 TTL (22 CPU, 12 GPU), 1 ROM, 1 RAM, 1 PAL, 4 analog.
  • Gate Count: 1,425 (935 CPU, 490 GPU)
  • PCB size: 8" x 5" (200 x 125mm) double-sided board.
  • Power: 6v @ 1.6A (10W)

Here’s a presentation as a Google doc - from 2023 VCF East this weekend.

There might yet be a kit for sale - keep an eye on the website:

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Long long ago, MIT had an intro to computer architecture course that required every student to build a computer using TTL chips. It all fit on a breadboard-system-in-a-suitcase called a “nerd kit.” They showed us some mercy by putting the ALU, DRAM, and UART on little PCBs. Everything else we had to wire up by hand. A fair bit of minimalization was achieved using lots of vertical microcode that was written by a TA who slept in his office and rarely came out. I think it all fit on four solderless breadboards

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Video of this talk is now up:

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