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Motorola 6800

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Re: Motorola 6800

#41

Post by FullyFunctional »

self wrote: post #5
FullyFunctional wrote: post #2

With the optics of _compiled_ code, how do the various 8-bitters stack up? (6809/6811, 65C02, Z80, H8, ...)? One would have to account for the frequency allowed by the ISA at iso-technologies (which makes including AVR somewhat tricky). I only have experience with Z80 and 65C02 and I believe the consensus is that a 4 MHz Z80 beats a 2 MHz 65C02, but neither is a particularly nice compiler target.

Some of that can be gleaned from this benchmark, published in Byte, in 1981: https://en.wikipedia.org/wiki/Byte_Sieve Results for a few 8/16 bit processors are here (and on subsequent pages): https://archive.org/details/byte-magazine-1981-09/page/n193/...

Very cool. While obviously not ideal, the results are probably accurate within a small factor. Unfortunately there's no assembly version for 65C02 but Z80 does surprisingly well in this test.

I muse what could be done with modern cross-compiler (SAT solving for optional code sequences?) A llvm backend for Z80 has recently kicked back into gear: https://github.com/jacobly0/llvm-project

Re: Motorola 6800

#42

Post by B1FF_PSUVM »

awful wrote: post #39

The Heathkit/Zenith ET-3400 trainers with 6800s, and the accompanying Heath/Zenith coursework, were fantastic in 1982. 50+ of us completed it that year, the class final was bit-banging the tune of "Anchors Away" as the instructor was a Navy officer and educator, retired to civilian teaching. I later learned machine language on broken superscalar mainframes as bit-chaser, but the 6800 were simply fantastic devices and…

> Flat, shared memory [...] nice op codes and indexing, as I recall.

Yeah, that was what the guy working with the Moto chips smirked at us slaving on Intel 808x contraptions, back in those days ...

Re: Motorola 6800

#43

Post by Salgat »

awful wrote: post #39

The Heathkit/Zenith ET-3400 trainers with 6800s, and the accompanying Heath/Zenith coursework, were fantastic in 1982. 50+ of us completed it that year, the class final was bit-banging the tune of "Anchors Away" as the instructor was a Navy officer and educator, retired to civilian teaching. I later learned machine language on broken superscalar mainframes as bit-chaser, but the 6800 were simply fantastic devices and…

I learned assembly on a 68HC11 heathkit, damn those things were awesome!

Re: Motorola 6800

#44

Post by Doctor_Fegg »

dymk wrote: post #9

I built a small multitasking kernel with a friend with a 68000 (m68000) in college. We implemented it on breadboards, I think with 30 or so feet of jumpers [0]. I had very little prior embedded experience, so it was trial by fire. It was a wonderful introduction to how kernels work (or at least concurrency and scheduling) at their most basic level, without having to deal with the complexity of virtual address spaces,…

> "Test condition, decrement, and branch". All in one instruction

The Z80 had that too - DJNZ (Decrement and Jump if Not Zero). Standard way of writing loops.

Re: Motorola 6800

#45

Post by kjs3 »

dylan604 wrote: post #30
klelatti wrote: post #26

Worth mentioning the 6501 which was launched by MOS Technology alongside the 6502 and was pin-compatible with the 6800. Motorola sued alleging patent infringement and misappropriation of trade secrets. MOS Technology settled, paid Motorola $200,000 and dropped the 6501.

$200k sounds like such a small number, but it was the dropping of the offending chip that was the gotcha.

Well...200k in 1975 $'s. And MOS was a startup, basically. So not a trivial amount. But yeah, a big part of the initial pitch was "you can use your same hardware design but replace the $300 CPU with our $25 CPU".

Re: Motorola 6800

#46

Post by mek6800d2 »

dymk wrote: post #13
pinewurst wrote: post #12

Earlier quoted context omitted.

The 6800 is nothing like the 68000.

Well, it was the predecessor :)

There was the 6809 in between. I remember BYTE magazine's cover story, "A Microprocessor for the Revolution". Well, not quite, as it turned out! :)

Re: Motorola 6800

#47

Post by drfuchs »

Doctor_Fegg wrote: post #44
dymk wrote: post #9

I built a small multitasking kernel with a friend with a 68000 (m68000) in college. We implemented it on breadboards, I think with 30 or so feet of jumpers [0]. I had very little prior embedded experience, so it was trial by fire. It was a wonderful introduction to how kernels work (or at least concurrency and scheduling) at their most basic level, without having to deal with the complexity of virtual address spaces,…

> "Test condition, decrement, and branch". All in one instruction The Z80 had that too - DJNZ (Decrement and Jump if Not Zero). Standard way of writing loops.

The IBM 360 had BCT back in 1964. Rumor had it that it was created for Fortran DO statements (“for-loops”), but IBM’s compiler never emitted it.

“The BCT instruction subtracts 1 from the value of the contents of the target register specified in the first argument. If the value in the target register after the subtraction is zero, no branch occurs. Otherwise the program branches to the specified address.”

Re: Motorola 6800

#48

Post by ataylor284_ »

Doctor_Fegg wrote: post #44
dymk wrote: post #9

I built a small multitasking kernel with a friend with a 68000 (m68000) in college. We implemented it on breadboards, I think with 30 or so feet of jumpers [0]. I had very little prior embedded experience, so it was trial by fire. It was a wonderful introduction to how kernels work (or at least concurrency and scheduling) at their most basic level, without having to deal with the complexity of virtual address spaces,…

> "Test condition, decrement, and branch". All in one instruction The Z80 had that too - DJNZ (Decrement and Jump if Not Zero). Standard way of writing loops.

The 8080 lacked this, but even though the 8086 was more or less based on the 8080, this probably inspired the 8086 LOOPNZ instruction. Same idea, hardcoded to use the CX register instead of B on the Z80. The unoffical nicknames for the AX, BX, CX, DX were accumulator, base, count, and data. CX was used for the count for all looping and string move instructions. Similarly, BX was special purpose for indirect operations and AX/DX for certain logic and arithmetic instructions.

Re: Motorola 6800

#49

Post by mtnygard »

engineer_22 wrote: post #4

I just finished an undergraduate class on microcontroller applications that used a MC68HC12 dev board. We coded in Assembly and then later in C. I'm curious, is this a typical platform in other computer engineering programs in the US?

I had a similar course using the 68HC11... but that was in 1991 or '92. I am (pleasantly) surprised to hear that this kind of class is still running. Haven't done embedded for a long time, so I don't know if the 68HC12 is current or not.

Wouldn't worry thouhg. Even if that chip is not in wide use now, the skills you learned are transferrable to any other.

Re: Motorola 6800

#50

Post by bitgif »

The Space Shuttle Main Engine built by Rocketdyne uses redundant M68000 processor to control the engine. I would say I was lucky to have chance to work on a system that has a great function such as SSME
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