Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [6809]

For questions regarding the Motorola 6809 microprocessor.

11
votes
2answers
3k views

Why was the 6809 so expensive?

The 6809 was released in 1978, but looking at the usual source for price quotes for old computer components, Byte magazine, I cannot find any quotes for 1979. December 1980 lists it at $38, compared ...
7
votes
2answers
659 views

How useful were the 6809/6309's indirect addressing modes?

Much like the VAX, the 6809 and 6309 have a preponderance of indirect addressing modes (in VAX parlance, "deferred"), though neither go so far as to include a VAX-like doubly-indirect mode. To what ...
6
votes
2answers
387 views

Hardware multipliers on classic CPUs

Can anyone offer some back-of-envelope sort of estimates of what sort of gate count was needed to add a multiplier to 8-bit CPUs? I ask because I find it a bit odd that the 6809 had one, but none of ...
11
votes
4answers
488 views

Motorola 6809 two stacks design

I'm an assembly newbie, but I'm curious about why the designers of the 6809 choose to use 2 stack in the microprocessor architecture. What is their original intent? The Wikipedia page says "a user ...
29
votes
4answers
6k views

What limited the use of the 6809 CPU in personal computers?

Why did manufacturers of home computers avoid using the 6809 CPU? I realize that the Z80 and 6502 had a 3- or 4-year head start in availability. But once it did become available in 1978, I don't ...
7
votes
1answer
81 views

HD63B03R timer interrupt frequency

I am trying to maintain an old procuct for my employer, based on an HD63B03R which is a 6800-style micro. The crystal on the PCB generates a 4.75MHz clock. I believe from the data sheets found on t'...
13
votes
1answer
361 views

Calculating the time for a CPU cycle

As a learning exercise, I'm writing an emulator for the 6809 CPU. I'd like to simulate the speed of the CPU. I know the Motorola 6809E runs at 0.895 MHz and 1.79 MHz on the Color Computer 3. How do I ...
15
votes
1answer
473 views

Motorola 6809 Stack Blasting

I've seen several mentions of a "Stack Blasting" technique for copying memory quickly on the 6809. What is it? How does it work?
32
votes
3answers
909 views

Advantages of a Hitachi HD6309 versus a plain Motorola MC6809

Hitachi was a second source for the Motorola 6809 Micro Processor. The 6309 had many secret features. What advantages does the HD6309 have over the MC6809?