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Questions tagged [motorola-68000]

for questions about the Motorola 68000 microprocessor

6
votes
1answer
215 views

How to integrate an 512kB EEPROM on a A3660 accelerator board at $00F00000?

I am currently experimenting with Chucky's re-engineered A3660 accelerator board for the Commodore Amiga (3000(T) and 4000(T)). My ultimate goal is to add an additional 512kB EEPROM to the ...
4
votes
2answers
202 views

Motorola MACSBUG source code?

Does anyone know of a source for Motorola's MACSBUG 68k monitor source code (which was the basis for the classic Mac debugger with the same name)? I seem to remember it was available on the old ...
10
votes
5answers
938 views

Was there ever a genuine “mainframe-on-a-chip” microprocessor?

In the 1980s and 90s, there was a fad among the IT industry press to dub the newest "hot" microprocessor on the market as being a "mainframe-on-a-chip". I have seen this fawning description applied to ...
13
votes
3answers
2k views

Replacing 80286 with 68000

Suppose you wanted to take a 286 PC and replace the CPU with a 68000, not at the initial design stage, but actually modifying the finished machine, on the theory that they both have 24 bits of address ...
5
votes
1answer
187 views

Collection of older EPROM IC's

I acquired a collection of older EPROM IC's and am wondering what the rarity of them are or if they are rather common. Do people collect these items? 89142 NM27C512Q ~~ B9212 NM27C512Q ~~ B9312 ...
13
votes
2answers
868 views

68000 and memory access speed

On the one hand, I get the impression that memory chips around 1980 could be accessed no faster than 2 MHz. On the other hand, the 68000, introduced in 1979, had a typical clock speed of 8 MHz. How ...
18
votes
5answers
1k views

Can a retro-computer be a useful way to learn computer-architecture fundamentals?

I've been reading about the fundamentals of computer architecture, but I think I could get a better grasp of the basics if I could could have an actual device to play with. I had considered building ...
13
votes
3answers
742 views

How did the original Apple Macintosh and Atari ST use protected mode?

The Macintosh, ST, and Amiga were all 68000 CPU systems released in 1984-85, along with their respective new Operating Systems. While this was 5 years before protected mode became commonplace on Intel ...
21
votes
4answers
3k views

How did the Apple II forward binary instructions to the Z80 software card with CPM?

Microsoft produced the Z80 Softcard for the Apple II enabling it to run CPM and many Z80 binary programs. This seems to be an unthinkable achievement. (For a kid who had an Apple IIe but was only a ...
15
votes
8answers
2k views

Were people building CPUs out of TTL logic prior to the 4004, 8080 and the 6800?

I've just finished reading Charles Petzold's book, Code: The Hidden Language of Computer Hardware and Software. In it Charles explains building relays into gates, gates into logic components, and ...
8
votes
3answers
503 views

What limits Amiga 68030/40/60 accelerators to 256 MiB of RAM?

Even today there are companies that still make accelerators for the 68000-based Amigas, but I've never seen any such accelerator with more than 256 MiB of RAM. If the 68030+ can address 4 GiB, then ...
14
votes
1answer
947 views

Sega Genesis/Mega Drive ROM Disassembler

I am looking for a disassembler that supports Sega Genesis ROMs. Ideally, any 68000 disassembler should be able to do this (IDA Pro supposedly does an amazing job but their demo version does not ...
21
votes
5answers
1k views

Why is the Amiga ROM at a high memory location, and RAM in low memory?

When a 68000 CPU powers up, it reads a few words at memory location zero to get the initial stack pointer and program counter. That suggests to me that a computer system designer would put the system ...