Subject:
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Re: mindstorms NXT and memory
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 10 Jan 2006 15:03:59 GMT
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Viewed:
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9404 times
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In lugnet.robotics, Alexander Sack wrote:
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In lugnet.robotics, Jordan Bradford wrote:
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I said that RISC machines (in general) are harder to program in
machine code. The ARM is as easy as any other processor to program
in high level languages.
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Do you mean machine code (binary) or assembly language?
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There the same.
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Obviously you’ve not coded in machine language, or you’d know they are not.
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I first learned
assembly language programming on a MIPS chip (RISC). I’ve also done it on a
Motorola 68HC11 (a microcontroller), and I’ve written both pure machine code
and assembly language for the Intel 8086. I much prefer the MIPS
processor, followed by the 68HC11, and dead last is any Intel x86 chip.
Bleah.
For machine code, pretty much any chip is “hard” to program.
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I guess my last post didn’t make it.
Fundamentally, Steve is correct that RISC is typically more complex to
program since it uses less general purpose registers and more complex
instructions (it tries to do more per clock tic than CISC).
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You misunderstand RISC and CISC. CISC instructions often combine data memory
references with arithmetic, logical, or brach capabilities. RISC machines do
not. RISC instructions try to do *less* per clock tick, thus the instructions
take less logic, and can run *faster*.
Typically RISC instructions are simpler than CISC instructions. Often RISC
architectures separate memory related instructions from arithemtic, logical,
branch or other miscelaneous instructions. RISC machines typically have many
more registers than a CISC machine. The SPARC machines that Sun makes (RISC)
gives you 31 general purpose registers which can be used for address or data.
Compare this with the 68000 CISC where you get 8 address and 8 data.
The reason that folks think RISC is more complex to program is that it typically
takes a few RISC instructios to emulate a CISC instruction. I don’t find it
more or less difficult, just different. I’ve done assembly on 8080, 8085, 8086,
80286, IMB 360, IBM370, IBM 390, 6502, 6800, 6811, 68000(all CISC), as well as
SPARC, and soon to be ARM7 (RISC). I find the orthoginality of RISC instruction
sets much nicer than the redundancy of CISC machines. Having worked on
simulation of future CISC and RISC products from the gates up, I find RISC a
much better machine design.
I’ve programmed a bit of machine code on IBM 370. What a pain.
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However, these days, the lines between CISC and RISC are pretty much gone
(Intel’s execution unit is RISC based converting the assembly you write into
micro-ops). Moreover, both ARM and MIPS are extrememly well documented and
understood so as many have stated, programming even at the assembly level is
not hard. The real issue with assembly is typically the hand building of the
final binary (with custom linker layout files which can get real complicated
depending on the architecture and complexity of the program).
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In most cases the toolsets are easy to come by these days thanks in large part
to GNU.
Kev
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Message has 1 Reply:
 | | Re: mindstorms NXT and memory
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| (...) If you are talking about the actual 1's and 0's that represent machine code then you are correct and I misinterpreted your last post, i.e. the binary. When people speak of binaries they are usually referring to something like an executable (...) (18 years ago, 10-Jan-06, to lugnet.robotics, FTX)
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Message is in Reply To:
| | Re: mindstorms NXT and memory
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| (...) There the same. (...) I guess my last post didn't make it. Fundamentally, Steve is correct that RISC is typically more complex to program since it uses less general purpose registers and more complex instructions (it tries to do more per clock (...) (18 years ago, 10-Jan-06, to lugnet.robotics, FTX)
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