Search found 186 matches

by Garth
Tue Feb 19, 2019 1:33 pm
Forum: General Stuff
Topic: The Difficulty of ARM Assembly
Replies: 57
Views: 27051

Re: The Difficulty of ARM Assembly

The 6809 had a really nice instruction set, but it didn't really perform any better than the 6502. The 65816 is a much better upgrade IMO, and the SuperCPU ran it at 20MHz over 20 years ago. Why does the 65816 perform better? Is it because the 6809 takes an extra instruction fetch on indexing instr...
by Garth
Tue Feb 19, 2019 1:56 am
Forum: General Stuff
Topic: The Difficulty of ARM Assembly
Replies: 57
Views: 27051

Re: The Difficulty of ARM Assembly

The 6809 had a really nice instruction set, but it didn't really perform any better than the 6502. The 65816 is a much better upgrade IMO, and the SuperCPU ran it at 20MHz over 20 years ago.
by Garth
Mon Feb 18, 2019 1:34 am
Forum: General Stuff
Topic: The Difficulty of ARM Assembly
Replies: 57
Views: 27051

Re: The Difficulty of ARM Assembly

65xx at 32-bit (or 16-bit for that matter) would work so much better if they just widened the data bus. You'd lose drop-in compatibility, but the alternative - which WDC seems to have chosen - is to let 65xx die chained to the archaic bus interface of the 6502. Imagine if x64 was still using the sa...
by Garth
Wed Feb 06, 2019 9:37 pm
Forum: NESdev
Topic: When have you used a language (C, etc.) instead of asm?
Replies: 13
Views: 7220

Re: When have you used a language (C, etc.) instead of asm?

For context: I've learned a good amount about writing a game in assembly, so I'm wondering if I should consider writing any parts of a game in a higher level language. Beyond what others have said, you can dramatically raise the level of assembly language by using macros, making the source code muc...
by Garth
Thu Jan 10, 2019 3:10 pm
Forum: General Stuff
Topic: Imagine haveing a 7mhz 6502
Replies: 26
Views: 10775

Re: Imagine haveing a 7mhz 6502

Imagine haveing a 7mhz 6502 For many years, all of them being made have been guaranteed for at least 14MHz, and the off-the-shelf ones usually top out around 25MHz, if the supporting parts can work at that speed. See WDC's data sheet at http://6502.org/documents/datasheets/wdc/wdc_w65c02s_oct_8_201...
by Garth
Thu Jan 03, 2019 11:43 am
Forum: NESdev
Topic: ASM indentation style
Replies: 22
Views: 7604

Re: ASM indentation style

IF_GE ; Is the value above 127? [Shouldn't that say "above 61"?] I think my reasoning was that at that place in the code we don't know which direction we've offset in. It could probably be reworked a bit, since I'm checking for direction twice, but I've left it that way for now since it works... :P...
by Garth
Thu Jan 03, 2019 12:45 am
Forum: NESdev
Topic: ASM indentation style
Replies: 22
Views: 7604

Re: ASM indentation style

I sort of follow what I'm used to from other languages just because it makes things easier for me to read and wrap my head around. I'm not super consistent with it but for me that's not really the point. I just want to be able to read and understand what I'm doing with the code, so with that I usua...
by Garth
Sat Dec 29, 2018 6:22 pm
Forum: NESdev
Topic: ASM indentation style
Replies: 22
Views: 7604

Re: ASM indentation style

I agree with many of the points above (although not all). I indent to make conditionals and loops obvious, and also things like what's between a PHA and PLA for example. I always indent at least three spaces. One or two spaces are just enough to make it look like you just got really sloppy at vertic...
by Garth
Sat Dec 08, 2018 10:39 pm
Forum: Newbie Help Center
Topic: A thread where I'm going to ask some math questions
Replies: 40
Views: 15497

Re: A thread where I'm going to ask some math questions

We had basically the same conversation on 6502.org, at http://forum.6502.org/viewtopic.php?f=2&t=5317 . Various code suggestions were made there.
by Garth
Mon Oct 29, 2018 12:01 pm
Forum: NESdev
Topic: I got obsessed with thinking about hex to decimal algorithms
Replies: 9
Views: 6071

Re: I got obsessed with thinking about hex to decimal algori

Not really sure the 65816 has anything to offer over a 6502.. True, but for this specific purpose, both the 65816 and an authentic 6502 have something to offer over the slightly cut-down 6502 in the 2A03: the ALU reacts to sed . I didn't comment on this earlier because I figured it was regarding th...
by Garth
Mon Oct 15, 2018 1:39 am
Forum: Newbie Help Center
Topic: Strategy for managing register values
Replies: 20
Views: 6187

Re: Strategy for managing register values

I've never had the problem mentioned in the head post, knock on wood. In fact, for me, macros have prevented loads of bugs and saved me a lot of time. I sense that in many cases others make very poor use of macros though. I'd have to see a lot of examples in order to identify a pattern of what's hap...
by Garth
Fri Oct 05, 2018 7:44 pm
Forum: Newbie Help Center
Topic: Simulating floating point
Replies: 13
Views: 3594

Re: Simulating floating point

May I broaden the scope to scaled-integer ? Because fixed-point is just a limited subset of scaled-integer arithmetic. The first half of the front page of the section of my website section on large look-up tables is an article about scaled-integer, showing how to do things with it that most people d...
by Garth
Fri Oct 05, 2018 7:31 pm
Forum: Newbie Help Center
Topic: Local variables - performance vs comfort
Replies: 7
Views: 6663

Re: Local variables - performance vs comfort

2. Slow and more comfortable - Use hardware stack, which is so-so for A register, but quite slow for anything else as it would require lda mem, pha, pla, sta mem for every variable You don't need to constantly be pulling stuff off the stack and putting it back on. Nor are you limited to just the by...
by Garth
Thu Sep 06, 2018 10:52 pm
Forum: NESdev
Topic: should the I flag be set while processing an interupt?
Replies: 4
Views: 3270

Re: should the I flag be set while processing an interupt?

See the 6502 interrupts article at http://wilsonminesco.com/6502interrupts/ , especially starting with 1.3 at the subtitle "GETTING TO THE NUTS AND BOLTS." Oh, and uh... Enjoy my outdated cartoons.