Ivan Svarkovsky's S3-MSX-PC is an open-source bare-metal MSX2+ emulator running on an ESP32-S3 microcontroller, forked from Retro-Go with significant hardware-specific optimizations. It outputs 64-color VGA at 640×480@60Hz using the ESP32-S3's LCD_CAM peripheral with a simple R-2R resistor ladder, and supports PDM stereo audio and USB keyboards. Key technical achievements include replacing the standard Z80 switch/case opcode dispatcher with Computed Gotos (Threaded Code) to avoid Xtensa branch predictor thrashing, pre-shifting MSX palettes to GPIO pin mappings, eliminating 400KB of PSRAM lookup tables in favor of 1-cycle integer bit-shifts, and a custom zero-heap streaming LZ77 compressor ('Delta-Stride LZ') that handles 4.4MB MSX machine state saves directly to SD card without heap allocation. The project targets ESP32-S3 boards with the ESP-IDF v5.4.4 framework.
