FRANK 386

Official page: frank.rh1.tech — hub for all FRANK boards and firmware.

i386 PC Emulator for RP2350 (Raspberry Pi Pico 2) with VGA/HDMI output, SD card storage, PS/2 and USB keyboard/mouse, NES gamepad, and audio output.

Based on Tiny386 by Chunhui He.

Features

• Full i386 (and partially i486/i586) CPU emulation with optional x87 FPU
• Up to 8MB RAM (using 8MB PSRAM)
• VGA and HDMI graphics output (text modes and graphics up to 640x480)
• Sound: AdLib OPL2, Sound Blaster 16, PC Speaker, Tandy, Covox, Disney Sound Source
• SD card support for floppy, hard disk, and CD-ROM images
• Runtime disk manager (Win+F12) for hot-swapping disk images
• Settings menu (Win+F11) for changing emulator configuration
• PS/2 keyboard and mouse input
• USB keyboard and mouse input (via native USB Host)
• NES gamepad support with mouse emulation mode
• Boots DOS, Windows 3.x, Windows 95, Linux, and more

Screenshots

FRANK 386 in Action

Supported Boards

This firmware is designed for RP2350-based boards with integrated VGA/HDMI, SD card, and keyboard input:

• FRANK - A versatile development board with VGA output
• Murmulator - A compact retro-computing platform based on RP Pico 2 (M1 and M2 variants)
• Olimex PICO-PC - Olimex RP2350 PC board
• Waveshare RP2350-PiZero - Waveshare RP2350 board

Hardware Requirements

• Raspberry Pi Pico 2 (RP2350) or compatible board
• 8MB PSRAM (required for extended memory)
• VGA or HDMI connector
• SD card module (SPI mode)
• PS/2 keyboard (directly connected) - OR - USB keyboard (via native USB port)
• Audio output (optional): I2S DAC or PWM

Note: When USB HID is enabled, the native USB port is used for keyboard/mouse input. USB serial console (CDC) is disabled in this mode; use UART for debug output.

Board Configurations

Four GPIO layouts are supported: M1, M2, PC (Olimex), and Z2 (Waveshare).

VGA / HDMI

SD Card (SPI mode)

PS/2 Keyboard

PS/2 Mouse

NES/SNES Gamepad

I2S Audio

SD Card Setup

Directory Structure

Create a 386/ directory on your SD card:

SD Card Root/
└── 386/
    ├── config.ini      # Configuration file
    ├── bios.bin        # SeaBIOS ROM (required)
    ├── vgabios.bin     # VGA BIOS ROM (required)
    ├── dos622.img      # Hard disk image
    ├── boot.img        # Floppy image
    └── ...             # Other disk images

BIOS Files

Download SeaBIOS and VGA BIOS from the SeaBIOS releases or use bios.bin/vgabios.bin from sdcard/386.

Configuration File (config.ini)

Create 386/config.ini:

[pc]
mem=8M
bios=bios.bin
vga_bios=vgabios.bin

[frank-386]
cpu_freq=504
psram_freq=166

Preparing Disk Images

Floppy Images (.img):

• Standard 1.44MB floppy images (1474560 bytes)
• Create with: dd if=/dev/zero of=floppy.img bs=512 count=2880
• Format with DOS or use pre-made DOS boot disks

Hard Disk Images (.img):

• Raw disk images up to 2GB
• Create with: dd if=/dev/zero of=hdd.img bs=1M count=512
• Use FDISK and FORMAT from DOS to partition and format

CD-ROM Images (.iso):

• Standard ISO 9660 images
• Use CD burning software to create ISOs from CDs

Loading Disk Images

At Boot: Configure disk images in config.ini as shown above.

At Runtime (Disk Manager):

1. Press Win+F12 to open the Disk Manager
2. Use arrow keys to select a drive (A:, B:, C:, D:, E:)
3. Press Enter to browse disk images in the 386/ directory
4. Select an image file to insert, or eject the current disk
5. Press Escape to close the Disk Manager

Changes made via Disk Manager are saved to config.ini automatically.

Controls

Keyboard Shortcuts

Settings Menu (Win+F11)

Configure emulator settings at runtime:

• Memory size (1-8 MB)
• CPU generation (386/486/586)
• FPU emulation on/off
• Sound devices (AdLib, SB16, PC Speaker, Tandy, Covox, MPU-401, DSS)
• PS/2 or USB Mouse on/off
• NES Mouse on/off (emulate mouse with NES gamepad D-pad, B=left click, A=right click)
• RP2350 CPU frequency and voltage
• PSRAM / Flash frequency

Settings are saved to config.ini and take effect after restart.

Disk Manager (Win+F12)

Manage disk images without restarting:

• Insert/eject floppy images (A:, B:)
• Insert/eject hard disk images (C:, D:)
• Insert/eject CD-ROM images (E:)

Building

Prerequisites

1. Install the Raspberry Pi Pico SDK (version 2.0+)
2. Set environment variable: export PICO_SDK_PATH=/path/to/pico-sdk
3. Install ARM GCC toolchain

Build Steps

# Clone the repository
git clone https://github.com/rh1tech/frank-386.git
cd frank-386

# Build with default settings (M2 board, 378MHz, PS/2 keyboard)
./build.sh

# Build for M1 board
./build.sh -M1

# Build with USB keyboard support
./build.sh --usb-hid

# Custom build
./build.sh -b M1 -c 504 -p 166 --debug

Build Options (build.sh)

Build Options (CMake)

Release Builds

To build all firmware variants:

# Interactive (prompts for version)
./release.sh

# With version number
./release.sh 1.02

This creates firmware files in the release/ directory:

• frank-386_m1_<version>.uf2 - M1 board (Murmulator)
• frank-386_m2_<version>.uf2 - M2 board (Murmulator)
• frank-386_pc_<version>.uf2 - Olimex PICO-PC
• frank-386_z2_<version>.uf2 - Waveshare RP2350-PiZero

Flashing

# With device in BOOTSEL mode:
picotool load build/frank-386.uf2

# Or use the flash script:
./flash.sh

Troubleshooting

"0 bytes of memory" during Windows 95 setup

Use setup /im to bypass memory check.

"Protection error" during Windows 95 startup

Use patcher9x.

Enable mapdrive.com support (redirector) to map SD-card to network-attached-drive H

Set redirector = 1 in config.ini.

No keyboard input

• For PS/2: Check keyboard connection and GPIO pins
• For USB: Ensure firmware was built with --usb-hid option

SD card not detected

• Ensure SD card is formatted as FAT32
• Check SD card module connections
• Verify 386/ directory exists on SD card

License

MIT License. See LICENSE for details.

Authors & Contributors

Mikhail Matveev & DnCraptor

• frank-386 port and development (2026)
• Repository: https://github.com/rh1tech/frank-386

Acknowledgments

This project is based on the following open-source projects:

Tiny386

• Project: Tiny386 - x86 PC Emulator
• Author: Chunhui He
• License: BSD 3-Clause
• Description: The core i386 CPU emulator and PC peripheral emulation (8259 PIC, 8254 PIT, 8042 keyboard controller, VGA, sound devices).

Pico-286

• Project: Pico-286
• Author: xrip
• License: MIT
• Description: RP2350 platform integration, disk management, VGA driver concepts.

QuakeGeneric

• Project: QuakeGeneric
• Author: DnCraptor
• License: GPL v2
• Description: RP2350 hardware integration patterns, Murmulator platform support, and PS/2 mouse driver implementation.

QEMU

• Project: QEMU
• Authors: Fabrice Bellard (2003-2017), Vassili Karpov "malc" (2003-2005), Joachim Henke (2006)
• License: MIT
• Description: PC peripheral emulation code including 8259 PIC, 8254 PIT, 8257 DMA, 8042 keyboard controller, PCI bus, PC speaker, VGA, and AdLib OPL2 proxy.

MAME FM Sound Generator

• Project: MAME
• Author: Tatsuyuki Satoh (1999-2000)
• License: LGPL 2.1+
• Description: FM OPL sound generator (fmopl) for AdLib emulation, forked from MAME and relicensed under LGPL.

inih

• Project: inih
• Author: Ben Hoyt (2009-2020)
• License: BSD 3-Clause
• Description: Simple INI file parser for configuration file handling.

SeaBIOS

• Project: SeaBIOS
• Authors: Kevin O'Connor and contributors
• License: GNU LGPL v3
• Description: x86 BIOS and VGA BIOS firmware.

FatFs

• Project: FatFs
• Author: ChaN (2014, 2021)
• License: FatFs License (BSD-style)
• Description: Generic FAT filesystem module for SD card access.

FatFs Utilities

• Author: Carl John Kugler III (2021)
• License: Apache 2.0
• Description: FatFs utility functions for error handling and result string conversion.

Raspberry Pi Pico SDK

• Project: Pico SDK
• Author: Raspberry Pi (Trading) Ltd. (2020)
• License: BSD 3-Clause
• Description: PIO SPI driver for SD card communication.