Retro486 Pro — Pure-JavaScript Intel 80486DX2 PC & Motherboard Emulator

A 100% browser-based, dependency-free Intel 80486DX2-66 PC, Motherboard & Modular ISA/VLB Adapter Card Emulator written in pure ES6 JavaScript. Runs real unmodified SeaBIOS, VGA BIOS, FreeDOS 1.3, and classic DOS games (Commander Keen 4, Wolfenstein 3D, Duke Nukem II, DOOM) directly in the browser.

▶ Live demo: https://jandej.github.io/e486-web/

• Full Intel 80486DX2 CPU + 80487 FPU (js/cpu_486.js, js/fpu_487.js)
  • Real Mode, 16/32-bit Protected Mode, Virtual 8086 (V86) Mode
  • 32-bit Demand Paging (CR0.PG, CR3) with 4096-entry hardware TLB
  • Hardware Task Switching (TSS), CPUID, BSWAP, CMPXCHG, XADD, INVLPG
  • Integrated x87 Floating-Point Unit (FPU487)
• AT / i440FX Motherboard & Chipset (js/retro_bus.js, js/bios_rom.js)
  • Dual 8259A Programmable Interrupt Controllers (Master/Slave PIC)
  • 8254 Programmable Interval Timer (PIT Channels 0, 1, 2 + PC Speaker + SeaBIOS PM Timer 0x3CC)
  • MC146818 CMOS Real-Time Clock & NVRAM
  • 8042 PS/2 Keyboard & Mouse Controller + A20 Gate (0x92 / 0x60)
  • Interactive 486 Motherboard visualizer with live address/data bus, IRQ lines, and 7-segment POST display
• Hot-Pluggable ISA / VLB Expansion Cards (js/cards/)
  • SVGA / Bochs VBE Display Card (vga_card.js): Text modes (03h), CGA (04h/06h), EGA/VGA Planar 16-color (0Dh/0Eh/10h/12h) with hardware Pel Panning & Split-Screen LINE_COMPARE, Mode 13h (320x200x256), Mode-X, and VBE LFB
  • EGA 64-Color Planar Card (ega_card.js) & CGA Card (cga_card.js)
  • SoundBlaster 16 + AdLib OPL3 Card (soundblaster_card.js): WebAudio synthesis, DSP DMA playback, configurable IRQ/DMA/Port jumpers
  • Multi-I/O Storage Controller (multio_card.js): Dual-channel ATA/ATAPI IDE (C:, D:, E: CD-ROM) + EMULINK Floppy Controller (A:, B:)
  • Port 80h POST Diagnostic Card (post_card.js) & live In-Browser Custom JS Card SDK
• Browser Persistence (js/storage_cache.js)
  • Automatically caches ROMs, floppy images, custom uploaded .img/.iso files, and dirty DOS disk writes in browser IndexedDB + localStorage
  • Persists hardware setup (RAM size, CPU speed, CRT bezel effects, installed slot cards, and mounted drives) across browser reloads

Start any static HTTP server in the project root:

npm start
# or: python3 -m http.server 8080

Then open http://localhost:8080/ in your browser.

npm test

├── index.html              # Main Retro486 Pro Hardware Lab UI
├── css/                    # CRT monitor, motherboard & storage bay styling
├── js/
│   ├── app.js              # Main emulator coordinator & UI bindings
│   ├── cpu_486.js          # Intel 80486DX2 CPU core (Real/PM/V86/Paging)
│   ├── fpu_487.js          # 80487 x87 Floating-Point Unit
│   ├── retro_bus.js        # System bus, PIC, PIT, DMA, CMOS, 8042, PCI
│   ├── bios_rom.js         # SeaBIOS & VGA BIOS loader + fallback ROM
│   ├── storage_cache.js    # IndexedDB + localStorage persistence engine
│   ├── cards/              # Modular ISA/VLB expansion cards
│   └── ui/                 # Motherboard, Storage Bay & Card Editor views
├── data/                   # SeaBIOS (bios.bin), VGA BIOS (vgabios.bin), FreeDOS 1.3 (dos.img)
├── extra_disks/            # Pre-bundled 1.44MB DOS game & utility floppy images
├── docs/screenshots/       # UI screenshots for documentation
└── tests/                  # Node.js unit test suites