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Motorola 6800

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Re: Motorola 6800

#21

Post by Gordonjcp »

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.

The 6809 is ridiculously suitable for running Forth, because you've got two stacks, a 16-bit accumulator, and you can implement NEXT in two instructions taking about three clocks each.

Re: Motorola 6800

#22

Post by jhallenworld »

hashmash wrote: post #19
cmrdporcupine wrote: post #6

Earlier quoted context omitted.

I just don't think any of the 8-bits made good compiler targets. At least not C compilers. Not enough registers, even in the 6809.

In theory, a smart compiler could make heavy use of the DP register (6809 feature) and then local variables within a compiled function could access these "fast" global variables instead. This was a common pattern when coding in assembly, and it's much faster than accessing variables off the stack. The function wouldn't be reentrant, but a compiler pragma could be used to enable/disable the DP mode. Declaring the loca…

I wrote a multi-tasking OS for the 6809 and used the DP to hold the current task ID: task local variables would be in the direct page.

Re: Motorola 6800

#24

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).

I had the multi pak and the external uart. The entry level price of the coco was low but I think I got most of the peripherals available for it, particularly the disks were crazy expensive. Adding it all up I must have spent more than I spent on the AT clone that replaced it ($1200)

In most ways the C-64 was a great machine but boy was the disk drive slow.

Re: Motorola 6800

#26

Post by klelatti »

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.

Re: Motorola 6800

#27

Post by exmadscientist »

shimonabi wrote: post #8
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?

At our company we still use a MC68HC11 for an industrial device.

Be careful -- they're rapidly going obsolete. No one wants to fab old EPROM processes, and no one wants to package PLCCs anymore. If it's neither of those, I think you've got a bit more time.

There are "compatibles" out there, and some of them are very good indeed, but they're not without their hassles.

Re: Motorola 6800

#28

Post by jhallenworld »

PaulHoule wrote: post #24
jhallenworld wrote: post #20

Earlier quoted context omitted.

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).

I had the multi pak and the external uart. The entry level price of the coco was low but I think I got most of the peripherals available for it, particularly the disks were crazy expensive. Adding it all up I must have spent more than I spent on the AT clone that replaced it ($1200) In most ways the C-64 was a great machine but boy was the disk drive slow.

Perfect system == 6809 + SIO from the Atari800 + C64 SID + IBM PC keyboard + C64 VIC or maybe V9938.

Re: Motorola 6800

#29

Post by cmrdporcupine »

hashmash wrote: post #19
cmrdporcupine wrote: post #6

Earlier quoted context omitted.

I just don't think any of the 8-bits made good compiler targets. At least not C compilers. Not enough registers, even in the 6809.

In theory, a smart compiler could make heavy use of the DP register (6809 feature) and then local variables within a compiled function could access these "fast" global variables instead. This was a common pattern when coding in assembly, and it's much faster than accessing variables off the stack. The function wouldn't be reentrant, but a compiler pragma could be used to enable/disable the DP mode. Declaring the loca…

The WDC C compiler for the 65816 takes advantage of this (relocatable direct page). And the relocatable stack. In fact I believe what it does is relocate the stack to at least partially overlap the direct page.

It's still an awkward target though.

Re: Motorola 6800

#30

Post by dylan604 »

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.
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