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Questions tagged [m68k]

For questions about processors in the Motorola 68k (68000 series) range. Commonly used in Amiga, Atari ST, Macintosh, Sinclair QL and Sharp X68000 computers.

5
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1answer
166 views

Macintosh System 6 on Quadra?

System 6 is not officially supported on 68040 Macintoshes, but has anyone successfully run System 6 on an early Quadra, e.g. the Quadra 700?
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2answers
325 views

How did multiply instructions work in the various 68ks?

pndc says about the 68000: the [...] MULU/MULS instructions are very slow, taking about 70 cycles. The exact number of cycles is data-dependent because the microcode uses an iterative algorithm....
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5answers
2k views

Are later 68000 variants backward compatible with earlier ones?

The 68020 is an improvement over the 68000 because it includes new instructions, possibly better speeds and so on. The 68040 is an improvement over the 68020 again for the same reasons, as is the ...
2
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1answer
774 views

Why does the Motorola 68000 series require a kernel for Linux installation

When attempting to install Debian Linux 2.0 Hamm (m68k build) on a machine with a m68k (Motorola 68000) processor, I get a Kernel image must be specified error. Why must a kernel be specified to boot ...
37
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1answer
3k views

How does the 68060 branch predictor work?

The 68060 had a branch predictor that improved the cycle count of branches that tended to go one way or the other. Apparently it did not handle branches that alternated or had some kind of pattern to ...
12
votes
3answers
1k views

What do the “byte-select signals” in the 68000 do?

Got a question about how the 68000 addresses memory. Wikipedia says: The 68000 has a 24-bit external address bus and two byte-select signals "replaced" A0. Here is an image of the chip's pins: ...
11
votes
1answer
150 views

68020 addressing mode suitable for page printing?

Wikipedia's article for MC68020 sports this paragraph: Addressing modes The new addressing modes added scaled indexing and another level of indirection to many of the pre-existing modes, and ...
44
votes
6answers
4k views

Are there any modern compilers that can generate Amiga/m68k executables?

I would quite like to resurrect my openkick project. As I note on that project's README.md, it is stalled because GNU GCC is not fit for purpose. Sadly, there do not seem to be any other modern ...