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Re: 6502

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Real Men can program a 6502 without using the Y Register. :)





Re: 6502
Guy Macon <http://www.guymacon.com writes:
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If Real Men were required to give up one index register, they would
prefer to give up the X register, as the Y register has better
addressing modes.

Re: 6502

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Not a problem. Most of those addressing modes have been ripped
out as well.  When you are shipping 100,000 toys per day,
cutting the cost by a penny or two is more important than a
few registers, adressing modes, and instructions.  :)



Re: 6502
snipped-for-privacy@mojaveg.iwvisp.com (Everett M. Greene) writes:
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Well, you don't really need TWO whole index registers, do you?
If I absolutely had to pare down an 6502, I'd get rid of the X
index register.  The "(FOO),Y" addressing mode is much more useful
than the "(FOO,X)" mode.



Re: 6502
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Why do you need X AND Y ? Sheer frippery, one will suffice.

Re: 6502
On 1 Sep 2004 17:52:12 -0700, snipped-for-privacy@larwe.com (Lewin A.R.W. Edwards)

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Why do you need index registers at all ?

A few bytes of free RAM for a self modifying table access routine
should be enough.

When we start eliminating registers, why not eliminating stack
pointers at the same time. There has been a few processors without a
stack pointer, so this should not be a problem.

Paul


Re: 6502
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You don't need addressable registers at all. A stack machine gets
along quite nicely with a SP and IP alone.

--
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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Re: 6502
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That's the whole point.  It's a tradeoff.  At some point deleting the
hardware for a register costs you more (due to increased RAM or ROM
size) than it saves.

Removing the stack pointer from the 6502 would probably be much more
expensive (in increased RAM and ROM size) than removing one of the index
registers.

It may well be the case that deleting one index register from the 6502
architecture is cost effective for some applications.  However, this
would depend on the applications and the implementation technology.  If
you made this decision today, you might find out that it is no longer a
win next year.

I doubt that anyone in this newsgroup has done a detailed analysis of
the cost-effectiveness of removing an index register from the 6502, and
most of us don't have access to nearly enough data to be able to do so.
Sunplus may well have done such an analysis.

Re: 6502
On 02 Sep 2004 18:24:03 -0700, Eric Smith

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Loss of the Y register was a problem as soon as Sunplus made a chip
with more than 256 bytes of RAM. I wrote a speech recognition
application for one such chip, and it required "creative" programming
to use the higher-addressed RAM.

--
Jim McGinnis

Re: 6502


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Otherwise know as a "supercomputer." <grin>


Re: 6502


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In the toy industry, it's only the CPU and RAM that are stripped down.
The ROM is almost always huge, because it is holding a lot of highly
compressed sound.  The program seldom uses 1% of the ROM.

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There is a simple algorithm that we use; pick the cheapest one.  If you
can't get the toy to do what you want, strip away features.  If that
doesn't work, put the features back in, move up one step in cost/capability
and repeat.




Re: 6502
Guy Macon <http://www.guymacon.com writes:
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That algorithm is insufficient when you are the semiconductor vendor
and are attempting to determine what you should put in the chip in the
first place.  A much more thorough analysis is required.

Re: 6502
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The discussion of removing one index register from the 6502
and its effect is interesting in that the 6520 was developed
as an improved 6800.  The second index register was one of
the major improvements.

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I know from experience of programming of a rather substantial
DP application for the 6800 was a royal pain with only one
index register.  The programming model used simulated a
second index register, resulting in a pseudo-architecture
that had an amazing resemblance to a 6809 well before the
6809 was announced.

Re: 6502
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IIRC it was an independent architecture.  MOS Technology (IIRC)
developed it and the 6500 simultaneously.  They withdrew the 6500,
which was a 6800 clone, under threat of suits from Motorola.

--
 "A man who is right every time is not likely to do very much."
                           -- Francis Crick, co-discover of DNA
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Re: 6502
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  The 6502 is a capable core, but never really made it into the Single
Chip FLASH Microcontroller sector.

  SST did actually release data on a Flash 6502 uC probably
2 years ago now, but they pulled it in favour of the 89C51.

  If you want to experiment/learn, look for the FLASH uC with on-chip
debug, and reasonably capable Analog operation, plus low cost eval/debug
systems.

Good candidates here are :
Silabs (ex Cygnal) - see
http://www.silabs.com/products/microcontroller/developmenttools.asp#dev

Most impressive in this lineup, is the $25 064 Kit, 2 x USB + 1MSPS 16
bit ADC + 64KF fast uC :
http://www.silabs.com/products/microcontroller/C8051F064EK.asp

A couple of their smaller cores are available in DIP packages.


Less capable, but with devices in more hobbyist friendly packages
( and still with on Chip Debug ) are the eZ8 devices

http://www.zilog.com/products/partdetails.asp?id=Z8F04A28100KIT

-jg


Re: 6502
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about a year ago I opened up a $20 modern electronic chess board (a
board with lights on it that you can play chess against, something
like this http://www.thechessstore.com/product/APK18SK ), anyway, I
expected a modern microcontroller, but it had a 6502, external memory,
big paper pc board, couldn't believe it, I guess they are making
6502's like nails, and probably cost as little. I'm always amazed by
cheap mass production engineering, there must be a program manager
with a bat standing behind each engineer "what! you are using a 39.001
cent PIC when you could be using a 38.999 cent 6502" whack on the head

Re: 6502

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Pretty much.  I think it's more fun to work on lower volume,
higher margin stuff.  OTOH, I can't walk into Target and see
something I worked on either...

--
Grant Edwards                   grante             Yow!  Hmmm... A hash-singer
                                  at               and a cross-eyed guy were
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Re: 6502



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It is being used in the new HP33S calculator released by HP this year but in
general it
has not been used much in recent years.  A great little microprocessor,
however.

Jerry
--
---------------------------------------------------------------------
-- Jerry Petrey   -   Senior Principal Systems Engineer
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Re: 6502
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Do you know who makes the one HP are using ?
-jg


Re: 6502

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Found it here : [SPLB31A] 256K Rom, 4K RAM, LCD,
http://w3.sunplus.com.tw/products/lcdcontroller/splb.asp
-jg


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