Search found 7887 matches

by rainwarrior
Sat Nov 28, 2020 5:15 am
Forum: General Stuff
Topic: Meaningfulness of division by zero in computer science
Replies: 6
Views: 131

Re: Meaningfulness of division by zero in computer science

I know that real math doesn't allow division by zero under any circumstances That's not really true. The default state of things, in math or computing, is that division by zero is "undefined". That means that in the general purpose case you really can't assign any meaningful value to X/0. Whether t...
by rainwarrior
Tue Nov 24, 2020 11:50 pm
Forum: NESdev
Topic: FDS homebrew ?
Replies: 39
Views: 13526

Re: FDS homebrew ?

No, the bypass technique skips the check for KYODAKU. It does not need to be present on the disk.
by rainwarrior
Tue Nov 24, 2020 7:16 pm
Forum: Other Retro Dev
Topic: DOS VGA Tricks
Replies: 26
Views: 603

Re: DOS VGA Tricks

For X zooming, can the horizontal resolution timing be adjusted per-scanline? Horizontal scanlines have to be more-or-less constant duration, so that can't be it. There are a choice of 4 different pixel clocks, but that's no-where near the 26 different apparent sizes I see in the video capture. It ...
by rainwarrior
Tue Nov 24, 2020 7:12 pm
Forum: General Stuff
Topic: Homebrews with female characters
Replies: 154
Views: 31618

Re: Homebrews with female characters

It was just a joke about the test build DRW sent me once where all the dialog had been replaced with the letter A. :S
by rainwarrior
Tue Nov 24, 2020 6:06 pm
Forum: General Stuff
Topic: Homebrews with female characters
Replies: 154
Views: 31618

Re: Homebrews with female characters

DRW wrote:
Tue Nov 24, 2020 5:18 pm
Amy is not a blank slate or a silent protagonist, but has certain characteristics that are shown in the way she talks.
That's weird, all I remember her saying was AAAAAAAAAAAAAAAAAAAAAA.
by rainwarrior
Tue Nov 24, 2020 5:07 pm
Forum: Other Retro Dev
Topic: DOS VGA Tricks
Replies: 26
Views: 603

Re: DOS VGA Tricks

Even if your CPU is fast enough, your video card might not be, especially for 256-color graphics. For 60Hz 320x240, you need to write around 4.4MB/s to update the entire screen, and that's assuming you can double-buffer (so you don't need to wait for vblank) and don't need to spend any CPU time doi...
by rainwarrior
Tue Nov 24, 2020 4:32 pm
Forum: Other Retro Dev
Topic: DOS VGA Tricks
Replies: 26
Views: 603

Re: DOS VGA Tricks

There's the hardware split screen register (3d4 idx 18h) which resets scrolling to 0 at a configured time. I'm not clear if there's enough else. There's all the effects in Copper ... Ah! So there was a separate register to reset it! Interesting. That demo looks really cool. Though... sadly I tested...
by rainwarrior
Tue Nov 24, 2020 2:38 pm
Forum: Other Retro Dev
Topic: DOS VGA Tricks
Replies: 26
Views: 603

Re: DOS VGA Tricks

I heard that 60hz 320x240 actually does have quite a bit of flicker, at least on actual DOS machines. 60hz is better for modern monitors, though. I don't know why you've heard that? 60hz looks perfectly fine on old monitors. CGA and EGA cards were also 60hz at 320x200. 60hz was never a problem. If ...
by rainwarrior
Tue Nov 24, 2020 3:20 am
Forum: Other Retro Dev
Topic: DOS VGA Tricks
Replies: 26
Views: 603

Re: DOS VGA Tricks

Also, I really appreciate David Brackeen's excellent VGA programming tutorial which has been online for more than 20 years now:

http://www.brackeen.com/vga/index.html
by rainwarrior
Tue Nov 24, 2020 2:42 am
Forum: Other Retro Dev
Topic: DOS VGA Tricks
Replies: 26
Views: 603

Re: DOS VGA Tricks

I second Oziphantom's suggestion. Also the book is online for free: https://www.drdobbs.com/parallel/graphics-programming-black-book/184404919 I used Mode X for a recent port I made of my NES game. One of the consequences of 320 x 240 is the refresh rate lowers to 60hz instead of 70hz, which is prob...
by rainwarrior
Wed Nov 18, 2020 11:54 pm
Forum: NESdev
Topic: How do you publish an NES ROM?
Replies: 17
Views: 3941

Re: How do you publish an NES ROM?

I haven't reviewed it myself, but this very recently published fork of FCEUX is apparently attempting to make steam publishing of NES ROMs easy:

NEStek: https://lowtekgames.itch.io/nestek
by rainwarrior
Thu Nov 12, 2020 1:26 am
Forum: NESdev
Topic: 6502 vdelay - cycle delay routine with variable length at runtime
Replies: 37
Views: 8298

Re: 6502 vdelay - cycle delay routine with variable length at runtime

Ahh! Very interesting.

Version 10 is up now.

vdelay_short.s now is pretty much what you posted, but with vdelay_toolow rolled into vdelay_low to save a couple of bytes and keep under align 32.
by rainwarrior
Wed Nov 04, 2020 12:51 pm
Forum: NESdev
Topic: 6502 vdelay - cycle delay routine with variable length at runtime
Replies: 37
Views: 8298

Re: 6502 vdelay - cycle delay routine with variable length at runtime

So I discovered that 4 years ago Bisqwit added 2 articles to the wiki about fixed and variable delay routines. There are some very interesting ones here:

Delay Code: Callable functions

I think adjusted for the constraints they're 3 cycles faster and several bytes smaller.
by rainwarrior
Thu Oct 29, 2020 12:33 pm
Forum: Newbie Help Center
Topic: rol vs asl, whats the difrence
Replies: 5
Views: 1888

Re: rol vs asl, whats the difrence

Also, ROL/ROR are essential for multi-byte shifts:

Code: Select all

;16-bit shift
ASL low_byte ; high bit passes into carry
ROL high_byte ; carry passes into low bit
by rainwarrior
Fri Oct 23, 2020 11:58 pm
Forum: NESdev
Topic: 6502 vdelay - cycle delay routine with variable length at runtime
Replies: 37
Views: 8298

Re: 6502 vdelay - cycle delay routine with variable length at runtime

Okay, the split clc/sec optimization is in. I've also added the extreme versions. ( github ) I do think it would help the current 4 versions if the short version had a different label than the full version (e.g., vdelay vs svdelay). Normally I'd also suggest just putting them both in the same source...