I've done software for a long time, ranging from high level implementations of rendering systems, all the way down to GPU microcode but I've never really done any hardware design or implementation.

So I thought it would be a fun experiment to design and implement my own 8-bit computer system on an FPGA, starting with the CPU, and adding the graphics and audio subsystems. Along the way I added some other useful subsystems and here's a design what I came up with.

CPU

• 8-bit CISC processor running @ 12.5MHz
• 8 general purpose registers
• 5 special registers
• 858 opcodes
• Instruction set similar to Zilog Z80 and NEC 70K/0

Memory

• 64KB dual port RAM shared by the CPU and graphics unit
• 7 single port 16KB RAM banks accesible only by the CPU
• 16KB dedicated palette RAM
• DMA engine
• SD card controller

Graphics

• Maximum resolution: 320x240 @ 59.18560Hz
• Palette: 16 out of 4096 colors
• Dual playfield
• 7 graphics modes
• 8 32x32 sprites
• Horizontal scrolling
• Line parameter table
• VBL, HBL and raster line interrupts

Audio

• 4 stereo audio channels with antialiasing oscillators using polyBLEP and polyBLAMP
• ADSR and volume control per channel
• 5 waveforms: sawtooth, pulse, triangle, sine, LFSR noise
• 12dB lowpass/highpass/bandpass/bandstop filter per channel
• 2 delay units with 6dB lowpass filters
• Reverb unit

Aggression - Project SC Intro .mp4

Watch in YouTube

Release date: August 2024