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Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1258
BigEd wrote:
I can't find it now, but I'm pretty sure I read a story recently of an effort back in the day to write and debug a fast copy routine...

Found it: http://blog.moertel.com/posts/2013-12-1 ... -hack.html (it's 6809)
Cheers
Ed


Sat Jan 25, 2014 7:42 pm
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Joined: Tue Dec 31, 2013 2:01 am
Posts: 100
Location: Sacramento, CA, United States
BigEd wrote:

Nice link, Ed! The 6809 can be quite versatile in the hands of a true 8-bit hacker, but the technique described is very closely coupled to the 6809 architecture. Although I always somewhat admired the 6800 as "the grand-daddy" of all the 6xxx family (with which my brain feels the most comfortable) it can't be ignored that its instruction set can be brutally inefficient for some of the simplest tasks. Another example is pushing and pulling the X register:
Code:
... from Bob Uiterwyk's 6800 BASIC interpreter ...
 02CA DF 38    PUSHX   STX  PUSHTX
 02CC DE 3A            LDX  XSTACK
 02CE 09               DEX
 02CF 09               DEX
 02D0 DF 3A            STX  XSTACK
 02D2 36               PSHA
 02D3 96 38            LDAA PUSHTX
 02D5 A7 00            STAA 0,X
 02D7 96 39            LDAA PUSHTX+1
 02D9 A7 01            STAA 1,X
 02DB 32               PULA
 02DC DE 38            LDX  PUSHTX
 02DE 39               RTS
 02DF DE 3A    PULLX   LDX  XSTACK
 02E1 EE 00            LDX  0,X
 02E3 7C 00 3B         INC  XSTACK+1
 02E6 7C 00 3B         INC  XSTACK+1
 02E9 39               RTS
 

The 6809 equivalents would benefit by at least an order of magnitude from the availability of the U register, with a simple pshu X and pulu X.

Similar things can be stated regarding 6502 vs. 65802. Garth and saipan59 discussed this at length here, but the best message that I got from it is that the updated versions of each family were much improved from the originals, in a variety of ways.

Mike


Sun Jan 26, 2014 8:02 pm
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Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1258
BigEd wrote:
BigEd wrote:
I can't find it now, but I'm pretty sure I read a story recently of an effort back in the day to write and debug a fast copy routine...

Found it: http://blog.moertel.com/posts/2013-12-1 ... -hack.html (it's 6809)
Cheers
Ed

Because I landed on the previous page and had forgotten that I'd found the lost article, I went looking again. And found something similar for the Z80 in the Spectrum, for the game Starion, by David Webb, apparently. There's an interview with him here.


Fri Aug 21, 2015 8:26 pm
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