Minimig

Minimig 120x120mm PCB board

Minimig (short for "Mini Amiga") is an open source exact FPGA re-implementation of an Amiga 500.

Minimig started life in secrecy around January 2005 as a proof of concept type of deal by the Dutch electrical engineer Dennis van Weeren. He intended Minimig as the answer to the ongoing discussions within the Amiga community on implementing the Amiga Custom Chipset in FPGA and this was released under the open source license GPLv3 on the 25 July 2007.

Original prototype

The original Minimig prototype is based on the Xilinx Spartan-3 Starter Kit, the OCS chipset is synthesized in the FPGA. Two pcb boards are attached via the fpga kit expansion ports. The first one holds a 3.3V M68000 type CPU. The second has MMC memory card slot with the use of a small PIC microcontroller as acting disc controller that supports the FAT16 filesystem and does on-the-fly .ADF decoding.

     VGA-+-PS2  (joystick etc.)
         |
CPU <-> FPGA <-> Microcontroller <-> Flashmemory
         |
        RAM

The prototype was shown <ref> 060218 amigaroxx.zuurkool.com</ref> at an Amiga meet and loads most Amiga programs although bugs do exist. Coding is done in Verilog because Dennis found VHDL not to be his cup of tea. All done on a PC using Xilinx Webpack software.

Some users have suggested plans to make a joystick style direct-to-tv device for people wanting to play old Amiga games or run software. However a new single board version pcb has been designed, moving away from the Xilinx Starter kit.

Why

• Run Amiga specific application software to convert files to newer platforms.
• Run software only available on Amiga.
• Games.
• FPGA development experience using Verilog.
• Creating something for the community.
• Proof of Concept.
• Can create new games to take advantages of the new features in Minimig (faster memory, more memory sprites, colours, etc), while maintaining full compatibility with the classic Amiga.

Hardware

Platform

• Xilinx Spartan-3 400k gate (XC3S400-4PQ208C) FPGA using 60% capacity.
• Freescale MC68SEC000, 3,3V, at 7.09379 MHz. (However there's no 'E' clock, MOVE sr,<EA> is privileged and there is no real replacement instruction. This does not seem to affect any programs as of yet however.)
• Amiga ChipRAM bus and FastRAM merged into a single synchronous bus running at 7.09379 MHz.
• 2 MB 70 ns SRAM organised as 2 524288*16 banks.
• MCU PIC 18LF252-I/SP <ref> 070715 microchip.com</ref> (an alternative would be Atmel AVR) implements a FAT16 disclayout and handles loading of fpga configuration and kickstart. Simulates a floppy to the Amiga by encoding on the fly from .ADF files.
• MMC Flash memory card to load fpga configuration, kickstart and software for the simulated computer.
• 3× LEDs to display the MC68000 processor run status.
• Video D/A consists of 4 resistors for each color red, green, blue (4 bits/color) and output via VGA connector. <ref>Minimig schematics v1 Page3</ref>
• Audio from an 8 bit dithering sigma-delta converter with 2nd order analogue filter.
• +5V DC main power.

Ports

• Spare 4x generic I/O from the fpga
• JTAG for programming chips
• RS232 serial port
• 2x Joystick
• HD15F VGA video
• MMC Flash memory card slot.
• PS/2 connector Keyboard + Mouse
• 3,5 mm audio jack
• +5V DC 2,1 mm cylindrical dc plug power supply inlet.

Implementation

• OCS PAL video.
• 512 kB SRAM RAM for Kickstart used as ROM.
• 1,5 MB SRAM ChipRAM/FastRAM.

Roadmap

Date	Event
2005-03-06	Verilog sources coding started.
2005-12-05	Announcement of the project.
2006 Spring	Verilog sources completed.
2006-06-11	Screenshoot of schematic for board v1.0 published.
2006-10-15	Schematic for board v1.0 completed.
2007-06-xx	Sources predicted to be released, but weren't.
2007-07-04	Last source edit (core).
2007-07-13	Busy making website for the project.
2007-07-24	Minimig sources released on the official website.

Similar projects

On 2006-10-11 Jens Schönfeld at Individual Computers revealed that they have been working on a commercial Amiga in FPGA for the past year called "Clone-A" which is in fact similar to Minimig. In contrary to Minimig, Individual Computers's Clone-A is being developed by a three man strong development team that employ a full blown logic analyzer.

Will be using clone chips for CIAs, Paula, Gary, Agnus, Denise. CPU original motorola. Final chip will include AGA. Prize money incentive to find bugs. Might ship in late summer-2007. Working parallel port to allow 4-player games.<ref> 070309 amigaworld.net</ref>

Issues

• Needs a binary copy of kickstart from a real Amiga 500 due that it's copyrighted.
• Sprite engine still has bugs.

Tools

Computer to compile the project:

Shuttle barebone, Prescott Pentium 4 3 GHz, 1 GiB Ram, Software Xilinx Webpack version 6.3.03i (2007-07-22 9.1). Time from source .bit configuration file = 2 minutes. Cache and memory speed is vital for fpga software.

Feature

There has been suggestions for faster cpu, AGA graphics, harddisc, ethernet etc..

Free kickstart replacement (e.g. AROS)<ref>AROS Kickstart ROM Replacement bounty (Phase II) </ref>.

A discless version would eliminate the need for swapping flashmemories.

Minimig Improvements

See also

• Popek and Goldberg virtualization requirements
• C64 Direct-to-TV

External links

• Official Website including released code 'download-link'
• Official announcement
• Picture of completed Minimig rev 1.0 board (2006-11-15)
• Site with Minimig related pictures (Dennis + board at Commodore/Amiga shows) (under construction)
• Xilinx ISE Webpack
• AROS Kickstart ROM Replacement bounty (Phase II)
• AROS AmigaOS implementation download
• Announcement of the Minimig project (Amiga.org forum)
• The BoXeR project a Motorola 68040 75 MHz based motherboard.