|Minimig alternative cores|
Alternative coresThe minimig is a project designed by Dennis van Weeren his aim was to rebuild the Amiga500 inside an FPGA, so he build an FPGA board and described the Amiga’s logic in Verilog… a year later the Minimig was a fact. But why not use the Minimig hardware for other purposes as well, retro computing purposes to be correct. So instead of using Minimig1.bin (the default core), you can select any other core (that is ported to the Minimig board).
In order to support alternative cores you’ll need to have firmware on your PIC microcontroller that makes it possible to select the cores you want to use. This firmware release gives you the option to boot select an alternative core file even if this alternative core does not support the minimig’s OSD menu system. This is how it works: minimig starts including the loading of kickstart (user has now the possibillity of changing the mode and starting of an alternative core. A warm start (by pressing the reset button) now the system starts in the selected mode (which could be minimig mode or alternative mode)
Sometimes when developing/porting new cores for the minimig it might be possible that you select (and save the settings) of an non-functional core. In order to make sure that the settings can always be changed the system must be able to fall back to the default core and kickstart files (minimig1.bin and kick.rom). By holding the menu-button during reset the system will start in minimig mode with the default cores and kickstart. So now you can enter the OSD menu and select and save the proper core-file / kick-file and continue developing. This mode is an escape mode and normal user will never require this function. However it can also be usefull to switch back from alternative-mode core to the minimig mode without switching the minimig off-and-on.
Below you will find an VIC20 implementation for the Minimig board, the original VHDL design is to be found at FPGA arcade (MikeJ - jam 2008)
Downloads<click here to go to the download section>
minimig is a project designed (around
2006) by Dennis van Weeren who is an excellent
electronic engineer. He designed AND build the first real working Amiga A500
an FPGA. Fortunately I was one of the lucky ones who got hold of such
board (the first batch of minimigs consisted of only 5 boards).|
This open source project is wonderfull for everyone who wants to relive the Amiga glory days on REAL hardware and not on an emulator but who also want to bennefit of modern electronics, storage media and the versitallity of an FPGA. As you can see on the picture of the minimig's PCB, it is very small. It holds a microcontroller for booting up the FPGA and controlling of the SD-card. It has some RAM and a 68000 processor. It can connect a PS2 mouse, keyboard and to a VGA monitor. Or for those who want to connect to a TV, using the proper cables it can easily connect to the SCART input of your TV. And last but not least... 2 mouse/joystick ports.
There are some spare IO-pins, which can be used to connect to future designs or IO functionality of alternative cores.
My Minimig enclosureIn order to use the minimig to it’s full potential and to protect it from curious people touching it... I decided to place it into a nice little box, I’ve added a small PCB that holds 2 audio amplifiers (for the Amiga’s stereo sound), some switches for system configuration and selection and a joystick connector extension to use the joystick connectors from the rear of the box instead of the side. I also added a small RGB LCD display. So now I can place the whole with a keyboard and mouse in a small corner on my desktop and I can look at it and enjoy this marvelous piece of technical engineering when ever I want. The minimig makes it easy for me to play clasical Amiga games on a real machine instead of an emulator.
The minimig is one of the most impressive projects I’ve seen. Knowing that Dennis didn't know anything about programming FPGA’s when he began the project and seeing the result one year later. I’m impressed. And then also keep in mind that he did it all on his own, no help from others, just books, the internet and a lot... a lot of patience. He did not have access to fancy logic analysers and only worked in his spare time. If you consider that in 2006 there were companies trying to achieve the same goal and bragged about it. But Dennis didn’t bragg, he just build it. No fancy demonstrations, no fuss, just a working Amiga inside an FPGA...
The minimig functions very nicely and gives you the feeling you’re using a real Amiga. Minimig... thumbs up!!!
PS: because the minimig is a real reconfigureable computer it can also be used to operate with different cores. A different core makes it a different computer, because an FPGA can actually change it's internal structure connections to all of it's logical components. Creating an entirely new/different processor and surounding logic. For example the porting of existing cores in order to work on the minimig (example: C64, VIC20) would make the Minimig a very versatile machine.