A developer built an FPGA reimplementation of the 3dfx Voodoo 1 GPU using SpinalHDL, a modern hardware description language. The post covers two key abstractions that made the project tractable: encoding the Voodoo's four register behavior categories (FIFO, FIFO+Stall, Direct, Float) directly in SpinalHDL's RegIf abstraction, and using a netlist-aware waveform query tool called conetrace to debug a subtle multi-stage rendering bug. The bug appeared to be a framebuffer memory-ordering hazard but turned out to be three stacked precision mismatches in W quantization, perspective texcoord rounding, and blend-factor destination color handling. The post argues that modern RTL tools reduce the cognitive load of hardware design by making architectural intent explicit and execution queryable.
