Retrochallenge 2022/10

Cat-644 Hardware

The Cat-644 is a computer I've been developing around an Atmega 644 microcontroller

• Started in 2013 - This might become a vintage computer before I complete it!
• Atmega 644, 20Mhz, 4k internal SRAM (possibly upgradable to Atmega 1284 with 16k SRAM)
• 128k bitbanged SRAM: used as VRAM and XRAM
• VGA output, maximum of 64 colors at 512x240, software cycle-counted race-the-beam
• PS/2 keyboard
• RS-232 serial port
• SD Card
• 11 Khz mono 8-bit sound output
• expandable SPI bus: some experiments have been done with SPI-based ethernet shield originally intended for arduino
• It has been 'hardware complete' for a long time, and I have test programs for each piece of hardware, and combinations of hardware. (VGA + sound + keyboard all together was hard)
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• In previous retrochallenges, I started writing an OS for this thing, in a mix C and Assembly.