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| Memory Addresses http://anycpu.org/forum/viewtopic.php?f=25&t=108 |
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| Author: | BigEd [ Sat Jan 25, 2014 7:42 pm ] |
| Post subject: | Re: Memory Addresses |
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 |
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| Author: | barrym95838 [ Sun Jan 26, 2014 8:02 pm ] |
| Post subject: | Re: Memory Addresses |
BigEd wrote: BigEd wrote: Found it: http://blog.moertel.com/posts/2013-12-1 ... -hack.html (it's 6809) 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 |
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| Author: | BigEd [ Fri Aug 21, 2015 8:26 pm ] |
| Post subject: | Re: Memory Addresses |
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. |
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