486Tang - 486 on a credit-card-sized FPGA board

February 7, 2026 · View on GitHub

486Tang brings the classic 486 PC experience to Sipeed’s Tang Console 138K by porting the excellent ao486-MiSTer core. It implements a 486SX-class system with VGA graphics, Sound Blaster audio, IDE storage, and solid DOS compatibility — all on your FPGA.

Performance: roughly a 486SX-20 (no FPU).
DOS 6.22 is very usable; dev tools like Turbo C and apps like MS Word for DOS run well.
Best suited for games from ~1992–1993 and earlier.

Highlights

486SX-compatible CPU core with full 16/32-bit instruction set
VGA graphics, upscaled to 720p over HDMI
Sound Blaster 16–compatible audio with OPL3 FM
IDE/ATA controller supporting disks up to 8GB
PS/2 keyboard and mouse emulation via host PC/Mac
Compact and throughtfully-designed board

Gallery

Gaming

_{Prince of Persia}

_DOOM

Toolbox

_{SD Card Creator}

_{Keyboard / Mouse over USB-Serial}

My blog post about the porting process of 486Tang.

Quick Start

What you need

Tang Console 138K
MicroSD card
HDMI display
A PC or Mac for the toolbox app

1) Download

Grab the latest release: https://github.com/nand2mario/486tang/releases and unzip it. You’ll find:

486tang.fs — FPGA bitstream
sw/486tang-toolbox.exe — Windows toolbox
sw/486tang-toolbox.app — macOS toolbox
sw/boot0.rom — BIOS (open source)
sw/boot1.rom — VGA BIOS
README.txt

2) Flash the bitstream

Use the Gowin IDE (see Sipeed’s guide) to program 486tang.fs into the Tang Console 138K’s flash. Use settings similar to this.

3) Prepare the SD card

486Tang currently boots entirely from the MicroSD card (BIOS, CMOS, disk image). There’s no TangCore menu integration yet.

To create the MicroSD card:

Launch the 486Tang Toolbox from the release.
Open the “SD Card Creator” tab and provide:
- boot0.rom (BIOS)
- boot1.rom (VGA BIOS)
- Your DOS .vhd virtual disk (for example, this MS-DOS 6.22 disk).
Write the generated sd image to your MicroSD card with a tool like balenaEtcher.

To create a DOS virtual disk from scratch:

# Create an empty 256MB VHD (can also be done in the toolbox)
dd if=/dev/zero of=dos6_256mb.vhd bs=1m count=256

# Install MS-DOS into the VHD using QEMU
qemu-system-i386 \
  -drive file=dos6_256mb.vhd,format=raw \
  -m 64 -L . -fda msdos6_22disk1.img

4) Keyboard and mouse from your PC/Mac

Control 486Tang via USB-serial:

Connect the Tang Console to your computer.
Launch the Toolbox → “Keyboard/Mouse” tab.
Select the serial port and click “Start Interactive Mode”.
Click the pygame window to capture the mouse; your input is forwarded to the 486.

5) Install games

If you have a game image (e.g., from the 0MHz DOS collection):

# Mount your DOS disk (C:) and the game disk (D:) in QEMU
qemu-system-i386 \
  -drive file=dos6_256mb.vhd,format=raw,index=0 \
  -drive file=game.vhd,format=raw,index=1

# Copy from D: to C:
xcopy /s /e d:\somegame c:\somegame

Troubleshooting

macOS Gatekeeper: if the toolbox won’t launch, try:

xattr -r -d com.apple.quarantine 486tang-toolbox.app

Performance expectations:
- Target games from 1992–1993 and earlier for smooth play.
- This is tuned for classic DOS titles, not late 486/early Pentium software.
Boot problems:
- Check boot0.rom and boot1.rom versions.
- Reflash the SD card image and verify the bitstream is programmed to flash.
How do I find the serial port?
- macOS: it typically appears as /dev/tty.usbserial*. To list candidates:
```
ls /dev/tty.*
```
- Windows: it appears as COM plus a number (e.g., COM3). Open Device Manager (Windows key + X → Device Manager) and check “Ports (COM & LPT)”.

LED diagnostics (optional PMOD)

If you have Sipeed’s LED PMOD, it helps visualize core status:

From bottom to top (LED[0] → LED[7]):

LED[2:0]: Boot stage (0→5). 5 means BIOS/CMOS loaded and CPU started.
LED[3]: Sound activity
LED[4]: DDR3 init OK. This may occasionally fail; power-cycle to retry.
LED[5]: Keyboard activity
LED[6]: SD card activity
LED[7]: Video activity

Credits

ao486-MiSTer team — original 486 implementation

—

Enjoy authentic 486 PC computing on Tang FPGAs!