Jtdcftul

Back in the day with my A2500/30, I always wanted to get the 68030 versions of software if I could because presumably I'd be able to get a few percentage more performance in some cases. However, I get the sense that most non-AGA software was always compiled with the 68000 as a target.

However, it would have been nice if I could have soft-kicked a Kickstart for the '020+ if I was running on the '030, but I don't recall ever coming across one.

Was there ever a KickStart built for 68020+ instructions? If so, were they only usable on the AGA machines or was it possible to run on an ECS A2000 (albeit with an A2630)?

Cloanto maintain a list of known Amiga ROMs, a few of which require a 68020 or even a 68020 + MMU. The associated FAQ suggests that some A3000 ROMs use 68030-MMU-specific instructions.

The Amiga Forever description of differences between Amiga ROMs says that most ROMs can be used on other systems, as long as the required CPU is available, and the ROM fits (the document assumes that the ROM is loaded as a ROM, not soft-kicked). An AGA ROM should boot an ECS system, but won’t support all the ECS features (and obviously the system won’t support the AGA features).

The Amiga Forever license allows using its ROMs in real Amiga computers, so that would be a not-too-expensive way for you to try various ROMs. (I haven’t checked whether it actually includes 68020+ ROMs).

The AmigaOS had a pretty small and specific set of features to allow the system to easily adapt to upgraded CPU's, either shipped in upgraded systems from Commodore, or added to the system using hardware accelerators. These did not rely on special binary versions of Kickstart. The main features were:

1. Floating point hardware support via dynamically linked math libraries. A major advantage of accelerated hardware was the FPU supported by or included with 020+ processors. This was used automatically by applications that used the system math libraries.


2. Use of SetPatch at system boot. This command patches the system software, and includes support for loading a CPU specific library from LIBS:, such as 68040.library. Since this happens at early boot, it allows any changes needed by the system to support the specific CPU to happen before applications are loaded.


3. Use of the CPU command. This can be run at boot, or any other time, to detect and exploit CPU specific features, including CACHE control, Burst memory access, and relocating Kickstart ROM to higher speed 32-bit RAM.

These features provide enough flexibility at boot time that it was never necessary to build Kickstart ROM images for specific CPUs. Essentially, Kickstart exists in 3 basic forms for: AGA Amigas, ECS/OCS Amigas, and the A4000T. The reason the A4000T is special is just the addition of a 2nd hardware interface for HDDs (IDE+SCSI).

As far as I know, the best thing to do for a 68030 Amiga with ECS is to include LIBS:68030.library on your boot disk, and run the CPU command to enable both DATA and INST caches and the FASTROM option. This should give you the stability you need from the patches and the increased performance.

None of this is to imply that you couldn't create a custom Kickstart for a 68030 based Amiga that included some modules compiled (or optimized) for that CPU in the ROM. It is possible, though not trivial to assemble your own Kickstart image using whatever modules you like. But few, if any, standard Kickstart modules ever warranted this special attention. And custom Kickstarts like this usually just included CPU specific patches for added stability - essentially moving some of the SetPatch functionality into the ROM.