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.
23
questions
10
votes
1
answer
825
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).
...
- 895
13
votes
1
answer
1k
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 ...
- 133
4
votes
3
answers
237
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 "⟨...
- 365
4
votes
2
answers
232
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 ...
- 365
4
votes
1
answer
532
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 ...
- 15.8k
2
votes
3
answers
824
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 ...
- 39
5
votes
1
answer
223
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 ...
- 895
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. ...
- 403
3
votes
1
answer
245
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 ...
- 2,131
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 ...
- 15.8k
21
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 ...
26
votes
6
answers
9k
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 ...
- 563
6
votes
2
answers
551
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 ...
- 15.8k
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, ...
- 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 ...
- 60.1k
5
votes
1
answer
411
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?
- 895
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....
- 38.2k
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 ...
- 38.2k
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 ...
- 2,425
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 ...
- 38.2k
14
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:
...
- 38.2k
11
votes
1
answer
229
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 ...
- 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 ...
- 10.8k