I meic pico V6

i-meic

(German version: README_de.md)

The i-meic is a modular, expandable single-board computer based on the Intel 8088 CPU.

The hardware aims to recreate an IBM PC using the simplest possible means. The PC compute core consists of the 8088 CPU and 1 MB of main memory. All input/output is handled by a Raspberry Pi RP2040 Pro Micro. That is faster, simpler and cheaper than classic peripheral chips.

What does "i-meic" mean?

The name is derived from the German description of the project:

Concept in brief

Classic 8088 systems require a large number of peripheral chips (clock generator, bus drivers, interrupt controller, DMA, floppy/HDD controller, video, keyboard, etc.). The i-meic replaces this entire set of peripherals with a single microcontroller: the Raspberry Pi Pico.

The PC compute core consists of:

• 1× Intel 8088 CPU (16-bit, 20 address lines)
• 2× SRAM of 512 KByte each → together 1 MByte (the maximum of the 8088 address space)

The Raspberry Pi RP2040 Pro Micro (ARM Cortex-M0+) takes care of:

• clock generation for the 8088 CPU (single-step / clocked operation)
• loading the BIOS into SRAM at startup
• the complete I/O processing (every read/write access to an I/O port is intercepted and serviced by the Pico)
• the serial connection to a host PC (screen, keyboard and drives are virtualized over the console)
• the ITP3 interface for modular expansion

This architecture is unusually powerful because the Pico runs at a significantly higher clock frequency than the historic 8088 peripherals and can therefore handle I/O operations very quickly.

System and data flow

This is how a runnable DOS computer is created from source code:

   ┌────────────────────────────────────────────────────────────────┐
   │  70_RON-BIOS-NASM …  BIOS.ASM  (8088 assembler, NASM)          │
   │        │  nasm -f bin                                          │
   │        ▼                                                       │
   │     BIOS.BIN  (pure 8088 binary BIOS, segment F800:0000)       │
   │        │  COM2INC  (see 60_FPC_Lazarus/25_LAZ_CLI64_COM2INC)   │
   │        ▼                                                       │
   │     BIOS.INC  (Pascal byte array  BIOS_ARR[…])                 │
   └────────┬───────────────────────────────────────────────────────┘
            │  gets embedded into the Pico firmware
            ▼
   ┌────────────────────────────────────────────────────────────────┐
   │  10_…/20_Lazarus_PICO…  Firmware (Free Pascal / RP2040)        │
   │        │  Lazarus / FPC                                        │
   │        ▼                                                       │
   │     imeic_dos.uf2   →   flash onto the Raspberry Pi Pico       │
   └────────┬───────────────────────────────────────────────────────┘
            │  Pico boots:
            │  1. loads BIOS_ARR into SRAM (F800:0000)
            │  2. clocks the 8088 CPU
            │  3. services all I/O requests (IORQ)
            ▼
   ┌────────────────────────────────────────────────────────────────┐
   │  i-meic board  (8088 + 2×512 KB SRAM)  ←── serial ───┐         │

Repository structure

Operating-system variants of the firmware: For the i-meic board there are several firmware variants that differ only in the I/O interface – currently DOS (…_DOS) and CP/M-86 (…_CPM86). The hardware and the ARM cross-compiler are identical in each case.

Quick start

1. Have the PCB manufactured

The ready-to-use Gerber data is located at 10_i-meic-pico_V6/10_KiCAD/gerber_i-meic-pico_V6.zip and can be uploaded directly to a PCB manufacturer. The schematic and layout for further development are in the same folder as a KiCAD project.

2. Flash the Pico firmware

Copy imeic_dos.uf2 onto the Raspberry Pi Pico (BOOTSEL mode).

3. Start the console and connect

Start CONSOLE64 (in the folder 60_FPC_Lazarus/20_LAZ_Console64_GUI64_Win64_Linux/bin/), set the correct COM port and 921600 baud, then power up the i-meic.

Requirements

• Hardware: Intel 8088, 2× SRAM (512 KByte), Raspberry Pi Pico or a compatible RP2040 module (footprints for several variants are provided), serial connection to the host
• Software (development):
  • KiCAD for the hardware
  • Lazarus / Free Pascal including the ARM cross-toolchain for the RP2040 (the Pico is an ARM microcontroller); the firmware runs "bare-metal" on the Pico
  • RP2040 libraries by Michael Ring as a basis (included in the units/ folder, adapted for this project – see the warning below), original: https://github.com/michael-ring/pico-fpcexamples
  • NASM for the BIOS (binaries are included)

Acknowledgements / third parties

• The Free Pascal libraries for the RP2040 come from Michael Ring: https://github.com/michael-ring/pico-fpcexamples. They were an important basis for this Pico/RP2040 variant. ⚠️ The libraries shipped in the units/ folder have been modified and adapted for this project and must not be replaced by the current upstream version (otherwise compilation errors will occur).
• NASM is used to assemble the 8088 BIOS (see LICENSE_NASM.TXT).

License

This project is licensed under the GNU General Public License v3.0 – see LICENSE. The BIOS and COM2INC additionally include the NASM license (LICENSE_NASM.TXT) for the bundled NASM binaries.