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.
27 questions
13votes
2answers
870views
Are there more different ways Motorola 68000 A-line and F-line traps were used than the Classic Mac way and the Lisa way?
On the Motorola 680x0 there are instruction opcodes beginning with an $A nybble or an $F nybble which are not implemented but can be trapped. Some platforms took advantage of these in their ...
- 8,064
6votes
2answers
2kviews
Why does the 68000 have Immediate addressing modes for byte-width instructions?
Motorola's 68000 has an instruction like ori.b #immediate, d0. This particular instruction is encoded as all zeroes, followed by a full 16 bits encoding an 8-bit immediate value. The instruction word ...
- 40.3k
11votes
2answers
1kviews
What file format was used for binary executables on Motorola 680x0 Macintoshes?
Current macOS binary executable files use a format called "Mach-O" and prior to that there was the PEF "Preferred Object Format", and Wikipedia says "It was optimised for RISC ...
- 8,064
11votes
3answers
2kviews
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 ...
- 1,282
10votes
1answer
1kviews
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). ...
15votes
1answer
2kviews
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 ...
- 153
4votes
3answers
279views
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
4votes
2answers
279views
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
4votes
1answer
579views
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 ...
- 16.8k
2votes
3answers
1kviews
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
5votes
1answer
300views
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 ...
30votes
1answer
5kviews
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
3votes
1answer
275views
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 ...
- 2,231
10votes
3answers
2kviews
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 ...
- 18.5k
22votes
7answers
6kviews
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 ...
