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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.

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Why did Steve Jobs choose the Motorola 68030@25 MHz for the first NeXT Computer in 1988 and not an Intel 80386DX@25 MHz processor?

Was the reason because he knew the 68K from the Macintosh, or were there other reasons that spoke in favor of the 68030 and the additional 68882 floating-point coprocessor? The i386, along with a 387 ...
Coder's user avatar
  • 1,068
10 votes
1 answer
953 views

MC68000: address error in initial PC

After an MC68000 processor is released from reset, it fetches the initial stack pointer and initial program counter from the vector table at addresses 0-3 (for the SP) and addresses 4-7 (for the PC). ...
Zane Kaminski's user avatar
14 votes
1 answer
2k views

GCC to make Amiga executables, including Fortran support?

I have been compiling some command line programs to run on the classic Commodore Amiga. I started with GCC on WinUAE which worked but I realised I didn't have the understanding of the memory stack and ...
Lee Volante's user avatar
4 votes
3 answers
257 views

Mac OS Classic install error "the installer document is unusable for installation [...]" (original disks message)

Attempting to upgrade Mac OS Classic 7.5.0 to 7.5.3 via floppies that have been tested successfully on a Performa 460... but things fail ominously on my IIsi with "This is not the correct "⟨...
0xF2's user avatar
  • 365
4 votes
2 answers
244 views

Drive icons for LaCie Tsunami

I am restoring a LaCie Tsunami 240 external disk for the Macintosh. I found a replacement Quantum LPS240 and the hardware side is well on its way. This drive displayed a custom icon in System 7 (a ...
0xF2's user avatar
  • 365
4 votes
1 answer
545 views

Were any 680x0 features specifically requested by a customer?

The Motorola 680x0 processor family was used in a variety of systems, including Apple Macintosh, Atari ST, Commodore Amiga, Sharp X68000, and Sinclair QL systems. Had any of these customers wanted a ...
DrSheldon's user avatar
  • 16k
2 votes
3 answers
895 views

M68k Big Endian to Little Endian

I'm trying to write a binary file using vasm68k_mot (Motorola 68k) writing File-Size and File-Offset everything goes well, except that M68K is Big-Endian, there's a way I can change to Little-Endian ...
Raoni's user avatar
  • 39
5 votes
1 answer
247 views

MC68030: does execution resume during or after cache burst refill?

The MC68030 processor is equipped with dual 256-byte instruction and data caches as well as a "burst" mechanism used to quickly load a cache line from RAM or L2 cache controlled by the ...
Zane Kaminski's user avatar
30 votes
1 answer
4k views

Why are the later revisions of the Motorola 68060 heavily sought after by Amiga fans?

I have come across a few sources online in forums and on YouTube information related to using the Motorola 68060 in Amiga accelerators and the difficulty in sourcing genuine late revision parts. ...
Dougvj's user avatar
  • 403
3 votes
1 answer
252 views

Porting of software from the m68k family architecture to the DEC VAX

I am looking for impressions, memoirs, articles, guidelines - everything that is possible about the unusual direction of software migration. I am interested in non-Unix related code, and preferably ...
Wheelmagister's user avatar
10 votes
3 answers
2k views

What performance increase did an Amiga typically get with an FPU?

After seeing this question, I reminisced about how my old Amiga 2500/030 had a 68882 FPU unit. I recall that the Amiga's floating point routine library was smart enough to detect if you had an FPU or ...
bjb's user avatar
  • 16.3k
22 votes
7 answers
5k views

Why were there no 32-bit versions of 65xx CPUs, or 64-bit versions of m68k CPUs?

I don't understand why Western Design Center made the 65816 a 16-bit upgrade to the 6502 but Commodore Semiconductor Group/MOS Technology didn't make their own variant & why neither company made ...
6502Assembly4NESgames's user avatar
26 votes
6 answers
10k views

Why are old CPUs like MOS Technology 6502 and Motorola 68000 considered better for real time systems applications than modern x86 based CPUs?

Reading the Wikipedia article about real-time computing, I found written that: Once when the MOS Technology 6502 (used in the Commodore 64 and Apple II), and later when the Motorola 68000 (used in ...
bobeff's user avatar
  • 563
6 votes
2 answers
589 views

Were any M68000 systems capable of generating a "spurious interrupt"?

When an interrupt occurs on a Motorola 68000-family processor, it enters an interrupt acknowledge state, which continues until one of three signals are asserted: An external device places the ...
DrSheldon's user avatar
  • 16k
0 votes
2 answers
1k views

Arduino Uno (ATMega328) vs Motorola 68000/68010 [closed]

Since ATMega328 is a microcontroller, and Motorola 68000/68010 is a CPU, we consider only the processor core - command execution speed, memory access speed, arithmetic speed, registers in RAM or CPU, ...
Alex's user avatar
  • 471
29 votes
3 answers
7k views

Why did Intel abandon unified CPU cache?

When Intel introduced the 80486 in 1989, they included their first on-chip cache, ostensibly to compete better with Motorola, who had been including on-chip caches for 5 years (MC68020, 1984). Unlike ...
Brian H's user avatar
  • 60.8k
6 votes
1 answer
430 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?
Zane Kaminski's user avatar
8 votes
2 answers
2k 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....
Omar and Lorraine's user avatar
22 votes
5 answers
4k 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 ...
Omar and Lorraine's user avatar
3 votes
1 answer
2k views

Why does the Motorola 68000 series require a kernel to be specified during 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 ...
Retro Gamer's user avatar
  • 2,435
41 votes
1 answer
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 ...
Omar and Lorraine's user avatar
15 votes
3 answers
6k 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: ...
Omar and Lorraine's user avatar
11 votes
1 answer
237 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 ...
user180940's user avatar
  • 3,716
61 votes
8 answers
9k 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 ...
pndc's user avatar
  • 11.4k