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Motorola 6800

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Re: Motorola 6800

#111

Post by cmrdporcupine »

FullyFunctional wrote: post #105
rahen wrote: post #32

Earlier quoted context omitted.

These processors were designed for assembly programming, hence their very CISC-y ISA. Some 8-bitters designed for compiled languages would be the AVR family.

That's too generous. They were primarily designed for what was easy to implement and what _could_ be handled in assembly. Also, 8080 was an evolution of the 4040 (and that owed much to the 4004). Z80 had to be compatible with the 8080... I know less of 6502 but most of them were designed about what could be done, not what would be easy to program.

I actually only recently learned that the 8008/8080 was in fact not based on the 4004/4040 instruction set. They used the same numbering system, but the ISA has little to nothing in common with it and in fact the 8008 project was in started before the 4004:

https://sites.google.com/site/microprocessorintel4004/8008-8...

Re: Motorola 6800

#112

Post by davidgould »

klodolph wrote: post #102
davidgould wrote: post #87

Earlier quoted context omitted.

> The project itself is terribly run--the maintainers recently pushed out an ABI change which broke everyone's code, but released it as a minor version bump. When was this? What version? Thanks.

SDCC 4.2.0, released Mar 8, 2022.

I don't think your comment about a breaking abi change on a minor point release is fair. Perhaps you have misunderstood the release number scheme? Every year around the first quarter they have one major release, ie 3.9, 4.0, 4.1, and now 4.2. A minor release would be like 4.2.1. There is no significance to the major digit, ie 4.0 was just the release a year after 3.9 and not otherwise special.

I'm not affiliated with the project, but I think would be unfortunate if someone was turned away using or contributing to the best or only opensource tool chain for a number of processors (eg the paduak family) because someone claimed the project was terribly run.

Please consider updating your comment.

Re: Motorola 6800

#113

Post by kjs3 »

deaddodo wrote: post #96
kjs3 wrote: post #45

Earlier quoted context omitted.

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".

There was also an argument that the 6501 was built as a sacrificial lamb so that when Motorola inevitably sued them, they would be able to keep the 6502 out of the case.

Do you have a source for this? I had always read the change in pin-out was initiated after Motorola went legal.

Re: Motorola 6800

#114

Post by krallja »

krallja wrote: post #74
jug wrote: post #64

Where does “6800” come from? I loved my Amiga and it had an MC68000 so I guess they just tacked on a zero for the 16-bit generation, but how were their series originally named?

Good question for retrocomputing.stackexchange.com!

https://retrocomputing.stackexchange.com/q/24734/11579

Re: Motorola 6800

#115

Post by PaulHoule »

jhallenworld wrote: post #20
PaulHoule wrote: post #7

Earlier quoted context omitted.

I had a TRS-80 Color Computer when I was kid which had one major drawback: it could only display 32 characters across the screen compared to 40 characters for the Apple ][, C64 and most others at the time. The Coco could run an operating system called OS-9 which was Unix-influenced and came with a good C compiler and also a bytecode interpreted structure basic called BASIC09. I know C compilers were really popular am…

The 6809 was nice, but I think the CoCo otherwise was crap. Aside from the 32 column display and awful color scheme, the built-in serial port was bit-banged. This meant that floppy drive and serial access could not happen at the same time. This is very relevant when trying to use OS-9. There was an external serial port as an option, but there was only one slot. So you also had to buy a slot expander (a Multi-Pak).

Note that hardware flow control makes the bit banger a lot more reliable than it would be otherwise.

I had the bit banger connected to a compact printing terminal from DEC that ran at 300 baud and had an acoustic coupler so you could log into 300 baud services with nothing but the terminal. There was not a lot of risk that this device would overflow your buffers.

Re: Motorola 6800

#116

Post by kjs3 »

mark-r wrote: post #53
kjs3 wrote: post #45

Earlier quoted context omitted.

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".

I knew a guy who tried to build a multi processor system with 16 6800s. Made a mistake with the power supply and ended up frying all of them.

That's seriously ambitious (tips hat). There were a number of folks that came up with dual processor designs back in those days playing on the observation that most 8-bitters (and many 16- and 32-bitters) could never utilize more than 50% of the available memory bandwidth. There's an NS32000 application note somewhere that describes such a design, and NS had datasheets for an NS32132 that was an NS32032 with added some support for such a system. I dunno if the NS32132 ever shipped, however.

Re: Motorola 6800

#117

Post by hakfoo »

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?

My CS programme (class of 2003) had one semester of assembly programming, either 68HC11 or 8086. I took the 8086 flavour and it was definitely designed around dev-board style development rather than expecting a rich BIOS/OS support environment.

There was a more embedded-focus "Computer Systems Engineering" degree option which involved a lot more assembly..

Re: Motorola 6800

#118

Post by FullyFunctional »

cmrdporcupine wrote: post #111
FullyFunctional wrote: post #105

Earlier quoted context omitted.

That's too generous. They were primarily designed for what was easy to implement and what _could_ be handled in assembly. Also, 8080 was an evolution of the 4040 (and that owed much to the 4004). Z80 had to be compatible with the 8080... I know less of 6502 but most of them were designed about what could be done, not what would be easy to program.

I actually only recently learned that the 8008/8080 was in fact not based on the 4004/4040 instruction set. They used the same numbering system, but the ISA has little to nothing in common with it and in fact the 8008 project was in started before the 4004: https://sites.google.com/site/microprocessorintel4004/8008-8...

Thanks I might misremember. Regradless, 8080 is still awful and they could have sone better with more foresight (which is easy to say so many decades later).

Re: Motorola 6800

#120

Post by Tor3 »

AnimalMuppet wrote: post #57
Tor3 wrote: post #36

Earlier quoted context omitted.

The 6800 definitely is a classic, yes. The classics included at least 6800, 6502, 8080, and Z80. (To some extent 8085, but as an "expanded" 8080 the Z80 dominated.) The four of them powered the most iconic systems at the start of the microprocessor "takeover" at the end of the seventies (at the same time as I entered my electronics education). The 6800 was kind of left behind by the others eventually, but was used in…

Was the 8085 ever used much as a microcomputer CPU? I've seen it as an embedded CPU, but I don't recall it getting much run as a general-purpose CPU.

I've only touched one 8085-based CP/M system myself. I don't think they were that common, certainly nothing compared to Z80 and 8080.
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