This is my first blog post in more than eighteen months, and while I’ve not been nearly as active tech-wise as previously, I am still porting cores to the Turbo Chameleon 64 (see https://www.patreon.com/coresforchameleon), and more recently I was kindly offered a prototype of the new SiDi128.

Normally I’d have declined, since most of the new FPGA platforms are far too complex for my tastes – but SiDi128 is oldskool. No Linux subsystem here – instead there’s an ARM microcontroller running a tight baremetal firmware which is an evolution of that used on the MiST, which itself can trace its origins back to the original Minimig. The FPGA is nice and big (nearly five times the size of the one on MiST) and the board has dual independent SDRAMs. In other words, a nice incremental improvement on the MiST without an explosion in complexity.

Slingshot on atari-forum, who is the primary core developer on MiST and SiDi128, had already ported the Minimig core to the new platform, and added support for the dual SDRAMs, placing Chip RAM, Kickstart, and slow RAM in one chip, and fast RAM in the other.

The expectation was that this would yield a nice performance boost – but it didn’t.

2020-12-10

It occurred to me recently that there is a lot of history in the Minimig project, with many people making important contributions over the course of some 15 years.

It also occurred to me that as developers come and go, and new users encounter the latest Minimig cores without having seen what came before, there’s a real danger that some of that history will be forgotten.

2020-09-22

I’ve just released an updated version of the MinimigAGA core for all three of my current target platforms – TC64 version 1, TC64 version 2, and MiST.

The core doesn’t have 100% feature parity between the three platforms, since the MiST has an onboard microcontroller to handle input and storage, while the Chameleon doesn’t. Having to implement an equivalent microcontroller in the FPGA makes some things harder – but other things easier.

For this reason, this time around the TC64 ports have a feature not yet available on MiST – experimental floppy drive sounds. To enable this, simply copy the drivesnd.bin file onto the SD card. If you don’t like it, just delete the file again – there isn’t (yet) a way to turn it on and off from the menus.

Other changes this time include the addition of a very basic LED Audio filter implementation – not accurate, but just good enough to make the going-through-tunnels sound effect in Lotus II work, and Slingshot on Atari-Forum has put some hard work into debugging the CPU core, and found an issue with stack frames which was preventing certain Graftgold games from working in ‘020 mode. His fixes to the CPU are included.

I’ve also made some timing tweaks on all three platforms so that all of them build with clean timing reports.

Turbo Chameleon 64 users can find the latest version of the core here

MiST users can find the latest version of the Minimig core at the official MiST binaries repository.

2020-09-12

After porting the MiST’s Minimig core to the Turbo Chameleon 64, I spent happy few weeks adding extra features including, most notably, RTG support. A number of people have kindly supported me in this endeavour, both directly via PayPal and also on Patreon – and I’m very grateful for this support.

None of this would have been possible without building upon the MiST’s AGA core, though, so it seems only right that I should port my improvements back to the MiST.

2020-07-12

If it’s seemed quiet here lately, that’s because I’ve been hard at work improving the Turbo Chameleon 64 ports of the Minimig core.

The two main features added since the last release are an experimential implementation of the Akiko Chunky-to-Planar converter which can be used by a handful of games to increase video performance, and an experimental P96 retargetable graphics driver.

2020-04-02

Over the last few days I’ve been attempting to replace the OpenRisc control CPU within the DE1 and DE2 Minimig cores with EightThirtyTwo – and it’s fighting me every step of the way!

Firstly, why do I want to do this? It’s a long story…

2019-03-21

I found out recently that there is now a second version of the Turbo Chameleon 64 cartridge for the Commodore 64. The reason for this is, apparently, that the Cyclone III FPGA that was used in the original design has been superceded and is difficult to obtain at affordable prices. For this reason Individual Computers have redesigned the cartridge to use a Cyclone 10 FPGA instead. The model chosen is essentially the same thing in a different package, so porting cores would simply be a case of recompiling with the new device and pinout as the target – except they’ve also taken the opportunity to make small improvements to the design. For this reason it now takes a little bit of work to port existing cores to the V2 hardware.

I now have an initial build of the Minimig core for V2 hardware, which is available as before on the Minimig TC64 Snapshots page.

Edit: Since the V2 hardware is likely to attract newcomers to the Chameleon platform, I should explain what to do with the two files in the snapshop archive:

• The fampiga_tc64v2.rbf file is the core itself, and needs to be flashed into the Chameleon cartridge using the Chaco utility.
• The OSD_CA01.sys file is the firmware for the secondary CPU core that runs the menu system and disk emulation, and needs to be written to the root directory of an SD card. The card will also need to contain a Kickstart image, named kick.rom

Another point to bear in mind is that the core doesn’t yet attempt to translate the C64 keyboard to the Amiga – so far just the run/stop key is used to toggle the OSD – so you will need a PS/2 keyboard to use the core for anything that requires keyboard input.

Source is availabe, as before, on github.