Posted By
JamesD
on 2013-07-31
01:35:50
|  Re: Z80 GUI: SymbOS
>> I'll take programming the Motorola 6803 or 6809 over either of those.
>They are very rare in the microcomputers. It's curious what were the systems based on these CPU?
The Tandy Color Computers and Thompson MO series machines use the 6809 and there were also multi-user systems running OS-9 or Flex. Flex is kinda like CP/M and OS/9 is more Unix like.
The Tandy MC-10 and Matra Alice series use the 6803. I read another machine did as well. I think the other was an early laptop and I *think* it looks like the one used as a prop in 'Air Wolf'' but I'm not sure if it's the same one. The 6803 is also used for a keyboard controller in the Thomson MO7 and as the ADAMNET controller on the ADAM.
FWIW, the 6803 *should* be able to run a version of Flex as well if there are no conflicts with the internal hardware.
>> Z80 assembler isn't bad.
>I only wrote that 6502 assembler is much easier. z80 is the obvious CISC but 6502 provides only base operations like RISC.
>
>> Let me just say that the ARM and 6502 are *not* alike.
>Let's see my points:
1. 6502, 6809, ARM don't waste cycles like i8080, z80
>2. http://en.wikipedia.org/wiki/ARM_architecture#History - ARM was developed by 6502 men for 6502 replacement
The 6502 was a 6800 like architecture reduced mostly to 8 bits to cut the die size to improve yield and lower costs. It also had some optimizations. But it has little to do with the reasons behind RISC.
RISC arouse out of a series of papers published back and forth between some professors from Stanford, Berkely, and another university in 1980.
The topic was whether to ad instructions to CPUs that support compilers better, or to simplify the instruction set to make it easy for compilers to generate code and to pipeline the beast and run it faster to make up for the larger code. Compiler optimization technology was still mostly peephole optimization at the time and many hardware concepts that are common now didn't exist yet.
RISC 1, MIPS, and an IBM CPU (I forget the name) were the first RISC chips, the first two were built in university labs at Berkely and Stanford. This was in 1981.
ARM came out of some guys from another university (Cambridge?) reading the articles published by the other guys and their chip came a few years later (85?) based on the RISC concept. Yeah, ARM was to replace the 6502 but the CPU was not based on the 6502 at all.
Wiki huh? Well, I happen to have a computer architecture book here written by a couple of the guys that wrote some of those papers on RISC and built one of the first RISC CPUs.
I think at least three early chapters mention RISC in the "Historical perspective" at the end of the chapters which is where I got my info.
The book is called "Computer Architecture A Quantitative Approach" and the authors are Hennessy and Patterson. Major University libraries should have a copy but I wouldn't buy a copy unless you plan on designing a CPU yourself or want to know more about computer architecture than any sane person should. 
>SymbOS looks impossible for 4MHz z80 but 1.8MHz C+4 or 2MHz C128 should be faster! >Why they don't publish the sources? GEOS sources are still unpublished too. IMHO It is very odd.
SymbOS runs fine on a 4MHz Z80 and that's where it originated; it's just not crazy fast like the 20+MHz machines.
There is about a 2.2 times speed difference between the 6502 and Z80 from the benchmarks I've seen. As to which is faster, it depends on how many wait states you are getting rather than just clock speed.
BTW, the 6809 was used heavily in video games. Williams games like Defender, Joust, Robotron, etc...
The 6809 and 6803 were used in many pinball machines, Bally is one manufacturer that used them.
@MMS
"Fortunately the 6502 allows the complete shut-down of CPU (with or without NMI)
Upgrading this ready concept to a newer HW + Symb OS could be a very nice project.
So mapping the gfx seems done by the system previously too, though I read that only 1MHz Z80 CPU was used"
If the signals are available on the +4 expansion port to halt the CPU and take over the computer then I suppose that's even easier. I knew there were Z80 carts but I didn't know how they worked.
If you have to run at the host system buss speed it might be better to see if the eZ80, pipelined Kawasaki copy of the Z80, or other pipelined derivative of the Z80 has compatible buss signals for those other designs. Then it could run at 1 instruction per cycle even at the slower clock speed. That might make the plug in cart faster than the 4MHz Z80 machines from back in the day. It won't be as fast as the FPGA or Turbo R but it wouldn't be a slouch my any means.
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