🚀 go-pugleaf

The 65816 book will soon be published by Brady. The author is David
Eyes. If you really want one badly, give them a call, you might be able to
bum a review copy if it is not yet on the shelves.

Western Design Center did the design. Unfortunately their app-notes
and other documentation are (last I looked) inadequte. The chip, on
the other hand, is very real and very fast.

re: dropping a 65816 into your Atari 800XL in place of the 6502, to
upgrade it to 16 bits:  Note that ANTIC (the screen display chip) is
also an 8 bitter, so you would have to confine your display RAM to
within 64K addresses.  That's a real bummer - because one of the real
advantages of lots of memory would be to have several alternate screens
in memory at once and switch between them for animation, etc.  Also,
having usable RAM above the display area violates Atari 8-bit software
architecture, which always puts the display area at the top of available
RAM - the extra memory would not be usable by most 8 bitter programs
(but you could make RAM disk(s) out of it).

Then there's the problem that none of the existing memory decoding
handles more than 8 bits.  Also, you'd have to find a place to put the
additional memory chips without destroying the RF shield - a packaging
nightmare.

Sounds like an awful lot of work to me, and when you finished up you
would still not be able to run ST programs because of instruction set
differences between the 65816 and ANTIC and their ST equivalents.
Unless you want the experience of tearing apart your 8-bitter and
learning something, I think you'd be further ahead to buy a new ST.  (Of
course, those of us who use our 8 bitters for word processing, game
playing and bulletin-board-calling don't really need 16 bits anyway...)

	Dan

-----------------------------------

In an article, Fleysher.wbst@XEROX.COM (Dan Fleysher) writes:
>re: dropping a 65816 into your Atari 800XL in place of the 6502, to
>upgrade it to 16 bits:  Note that ANTIC (the screen display chip) is
>also an 8 bitter, so you would have to confine your display RAM to
>within 64K addresses....

>having usable RAM above the display area violates Atari 8-bit software
>architecture, which always puts the display area at the top of available
>RAM - the extra memory would not be usable by most 8 bitter programs
>(but you could make RAM disk(s) out of it).
>
   Unless I'm mistaken, that's merely a convention.  The display memory
can be anywhere (subject of course, to the usual alignment restrictions).

>Also, you'd have to find a place to put the
>additional memory chips without destroying the RF shield - a packaging
>nightmare.

  Granted, a problem; but there are a *lot* of 800XL's out there with 256K
and 512K already. 

>Sounds like an awful lot of work to me, and when you finished up you
>would still not be able to run ST programs because of instruction set
>differences between the 65816 and ANTIC and their ST equivalents.
>Unless you want the experience of tearing apart your 8-bitter and
>learning something, I think you'd be further ahead to buy a new ST.  (Of
>course, those of us who use our 8 bitters for word processing, game
>playing and bulletin-board-calling don't really need 16 bits anyway...)

   I think you missed the point.  The chip would be faster if only you
take into consideration the fact that it could do memory transfers and
arithmetic in 16 bits.  I once attempted to alter the public domain
Small-C compiler to generate 6502 code, and I gave up when I got sick of
all the high-byte/low-byte garbage-- the compiler would have turned out
twice as big and twice as slow.  
   And who wants to run ST programs, anyway? (:-)

 - Joel ({allegra,ihnp4,seismo}!uwvax!uwmacc!oyster)
 
P.S. I'd like to change my "split the group" vote from a no to a yes, just
so the obnoxious amiga/mac/ham-radio cross(and mis)-postings go away.

>    And who wants to run ST programs, anyway? (:-)
> 
>  - Joel ({allegra,ihnp4,seismo}!uwvax!uwmacc!oyster)

This is what you get when you live in the water... ;-)

-- 
                           --- Rob DeMillo 
                               Madison Academic Computer Center
                               ...seismo!uwvax!uwmacc!demillo


     "...I suppose you find the concept of a 
         robot with an artificial leg amusing?"

                    -- Marvin, the Paranoid Android