The Amiga was a great game system in its day, but there were some titles it was just never going to get. Sonic the Hedgehog was one of them– SEGA would never in a million years been willing to port its flagship platformer to another system. Well, SEGA might not in a million years, but [reassembler] has started that process after only thirty four.

Both the SEGA Mega Drive (that’s the Genesis for North Americans) and Amiga have Motorola 68k processors, but that doesn’t mean you can run code from one on the other: the memory maps don’t match, and the way graphics are handled is completely different. The SEGA console uses so-called “chunky” graphics, which is how we do it today. Amiga, on the other hand, is all about the bitplanes; that’s why it didn’t get a DOOM port back in the day, which may-or-may not be what killed the platform.

In this first video of what promises to be a series, [reassembler] takes us through his process of migrating code from the Mega Drive to Amiga, starting specifically with the SEGA loading screen animation, with a preview of the rest of the work to come. While watching someone wrestle with 68k assembler is always interesting, the automation he’s building up to do it with python is the real star here. Once this port is done, that toolkit should really grease the wheels of bringing other Mega Drive titles over.

It should be noted that since the Mega Drive was a 64 colour machine, [reassembler] is targeting the A1200 for his Sonic port, at least to start. He plans to reprocess the graphics for a smaller-palette A500 version once that’s done. That’s good, because it would be a bit odd to have a DOOM-clone for the A500 while being told a platformer like Sonic is too much to ask. If anyone can be trusted to pull this project off, it’s [reassembler], whose OutRun: Amiga Edition is legendary in the retro world, even if we seem to have missed covering it.

If only someone had given us a tip off, hint hint.

Amiga and Atari fans used to lord over their Apple-eating brethren the fact that Cupertino never moved to the most advanced 68k processors — so for a while, thanks to 68060 accelerator cards, the fastest thing running Macintosh software was an Amiga (or Atari). After all these years, the Macintosh community is finally getting the last laugh, as [zigzagjoe] demonstrates an actual Macintosh booting with a 68060 CPU for the first time in a thread on 68KMLA. Video or it didn’t happen? Check it out below.

The Mac in question is a Quadra 650, which is a good choice since it was about the last thing Apple sold before switching to PowerPC, and ran the 68040 processor. [Reinauer] had already produced a 68040-to-68060 socket adapter (the two chips not being pinout compatible), so the hardware part of the battle was already set. Software, however? That was a different story, and where [zigzagjoe] put in the effort.

We’re spoiled by decades of backwards compatibility in the x86 instruction set; Motorola wasn’t as kind back in the day, and the 68060 isn’t fully compatible with the earlier 68040’s instruction set. They did provide a translation that [zigzagjoe] was able to build into his custom ROM, though, which is how he’s able to get the Mac to boot and install System 7.1, the newest version that would boot.

Alas, the full 66 MHz clock speed [zigzagjoe] proved unstable. To make branch prediction work, he had to clock down to 50 MHz. Considering the ‘040 clocked at 25 MHz in the Quadra 650, that’s still a considerable improvement in clock speed.

At 66 MHz and giving up branch prediction, DOOM runs at 16.4 FPS. It slowed down (14.3 FPS) at 50 MHz, and branch prediction. We expected branching to have a greater impact, but apparently not. While DOOM is perhaps not the best benchmark on this hardware, it does answer the most important question you can ask of any bit of kit: yes, it does run DOOM!

While Apple has long since abandoned the 68k in favour of PPC, x86, and finally their own implementation of ARM, there are always enterprising upgraders.