Probably Average Computer Emulator

"How far can I push this thing"

The last attempt technically booted Windows (1-3) on the RP2040-based PicoVision. This one tries to see how far I can get on the RP2350.

So far works enough to boot Linux (2.2 from Debian potato) and Windows 95. Some posts from when I first got it running are here (or here). Can also run DOS and last time I checked Windows 3.1 would start.

If you like your chips cooked it boots in a few minutes! (alt post)

Features

A comparison with the other repo that this started from:

Feature	PACE	This repo
CPU	8088 (4.77Mhz)	386 (as fast as it'll go) (+BSWAP for SeaBIOS)
Chipset	DMA/PIC/PIT/PPI	DMA (2nd controller missing), 2xPIC, PIT, "8042" for keyboard/mouse
Memory	640K + 6-8MB from Above Board	8MB - holes from BIOS and VGA memory
Keyboard	XT keyboard	AT keyboard
Mouse	Serial mouse	PS/2 mouse
Video	CGA	VGA (256K)
Sound	PC speaker	Non-functional PC speaker (whoops)
Floppy	4x	2x (mostly the same code, now with writing)
Other Disks	IBM Fixed Disk Adapter	Primary ATA controller (2x hard drive or ATAPI CD drive)

BIOS

Uses SeaBIOS for BIOS. The required files are bios.bin and vgabios.bin. If copying the files from a QEMU install, the file you want is vgabios-isavga.bin, if you're building SeaBIOS from source set VGA Hardware Type to Original IBM 256K VGA in the VGA ROM menu.

The location of these files depends on the frontend being used.

Downloads

Some builds are available in the artifacts of the latest actions run. The RP2350 builds have an embedded BIOS.

SDL3

For running on... a PC, the only dependency is SDL3.

Supports up to two floppy drives and two hard drives (or CD drives). The BIOS files should be placed next to the executable.

Building

cmake -B build -DCMAKE_BUILD_TYPE=Release .
cmake --build build

Command Line Options

• --bios name.rom - Specify an alternate BIOS file
• --floppyN name.img Specify an image file for floppy drive N (0-3)
• --floppy-next name.img Specify an image file to be loaded in floppy drive 0 later, can be used multiple times (RCTRL+RSHIFT+f cycles through)
• --ataN name.img Specify an image file for ATA disk N (0-1). .iso files will be set up as an ATAPI CD drive.
• --ata-sectorsN Sectors per track for ATA disk N. By default tries to guess a geometry that allows all sectors to be accessed.

For example:

PACE_SDL --ata0 hd0.img --floppy-next disk1.img --floppy-next disk2.img

would boot from hd0.img and allow installing something from the two floppy images later.

"Pico 2"

Theoretically any RP2350-based board with PSRAM and DVI/DPI output. The BIOS files should be placed at the root of the repository before building.

Building (Stamp XL + Carrier)

cmake -B build.pico2 -DCMAKE_BUILD_TYPE=Release -DPICO_SDK_PATH=path/to/pico-sdk -DPICO_BOARD=solderparty_rp2350_stamp_xl .
cmake --build build.pico2

Building (Pico Plus 2 + VGA Board)

cmake -B build.pico2 -DCMAKE_BUILD_TYPE=Release -DPICO_SDK_PATH=path/to/pico-sdk -DPICO_BOARD=pimoroni_pico_plus2_rp2350 -DEXTRA_BOARD=vgaboard .
cmake --build build.pico2

Other Boards

• Adafruit Fruit Jam (-DPICO_BOARD=adafruit_fruit_jam)

Config

Can be configured with a config.txt file at the root of the SD card. The option names are similar to the SDL command line options.

ata0=hd-potato.img
floppy0=disk1.img

If there is no config.txt, hd0.img is loaded as the first hard drive (if it exists).