Search found 349 matches

by ulfalizer
Sat Oct 19, 2013 1:18 am
Forum: NESemdev
Topic: 6502 RDY input
Replies: 2
Views: 2118

Re: 6502 RDY input

Pure speculation here, but it might be because the intended use of RDY is for reading from slow peripheral devices (hence "ready", as in "data ready"). In that scenario it doesn't make sense to stop on a write.

Maybe it was simpler to only support stopping in certain states as well.
by ulfalizer
Thu Oct 17, 2013 10:17 am
Forum: NESemdev
Topic: Original Mario Bros bug on my emulator?
Replies: 141
Views: 28744

Re: Original Mario Bros bug on my emulator?

I am the same way. Analog = voodoo. I understand pull-up, pull-down, and even to some degree filtering caps, transistors, and diodes. But beyond that, when I see a mesh of Rs and Cs and Ls and other crap I don't yet have the "oh yeah that's a bandpass filter at 1KHz" intuition. I have been wanting ...
by ulfalizer
Thu Oct 17, 2013 12:20 am
Forum: NESemdev
Topic: puNES Emulator
Replies: 766
Views: 1055880

Re: puNES Emulator (ex Fnes)

For an emulator that that does sprite evaluation and draws pixel-for-pixel, doing an additional pass over the OAM after each scanline has been drawn to the buffer and filling in sprite pixels would probably be a reasonable compromise to disable the sprite limit. Wouldn't catch stuff like switching b...
by ulfalizer
Wed Oct 16, 2013 11:04 pm
Forum: NESemdev
Topic: Original Mario Bros bug on my emulator?
Replies: 141
Views: 28744

Re: Original Mario Bros bug on my emulator?

I'll plug my (with help from lidnariq and Quietust and others) Visual * circuit reading tutorial in case you haven't seen it: http://wiki.nesdev.com/w/index.php/Visual_circuit_tutorial . I can read digital (NMOS) circuits decently now, but am still pretty lost when it comes to many analog aspects of...
by ulfalizer
Sun Oct 13, 2013 10:47 pm
Forum: NESemdev
Topic: SDL slowness while scrolling in Firefox on X11
Replies: 10
Views: 3893

Re: SDL slowness while scrolling in Firefox on X11

Played around with the SDL_VIDEO_X11_XINERAMA and SDL_VIDEO_X11_XRANDR environment variables, but no setting seems to eliminate the slowdown. Could be a problem below the SDL level. The SDL_VIDEO_X11_XRANDR documentation says "by default SDL will not use XRandR because of window manager issues" by t...
by ulfalizer
Sun Oct 13, 2013 6:48 pm
Forum: NESemdev
Topic: SDL slowness while scrolling in Firefox on X11
Replies: 10
Views: 3893

Re: SDL slowness while scrolling in Firefox on X11

I know, right? I can't tell you how many times I need to play SMB with the window half way between two monitors with the menu screen overlay open. It's so inconvenient and I'm considering moving to something else until SDL2 gets its act together. It happens with SDL1 too, and it's more about genera...
by ulfalizer
Wed Oct 09, 2013 9:30 am
Forum: NESemdev
Topic: SDL slowness while scrolling in Firefox on X11
Replies: 10
Views: 3893

Re: SDL slowness while scrolling in Firefox on X11

Split off emulation and SDL stuff into separate threads, and now the audio runs fine even though video framedrops like crazy with the Ubuntu menu open. Another thing it hates is when you place the window so it overlaps the border between two monitors. Robust stuff... :P
by ulfalizer
Tue Oct 08, 2013 3:05 pm
Forum: NESemdev
Topic: First steps in writing an emulator
Replies: 75
Views: 29748

Re: First steps in writing an emulator

@ulfalizer So by overlapping, you mean they happen at the same time? There's so many quirks that make this stuff hard to understand. I'm definitely gonna need to keep reading up on this stuff. Yup, the CPU carries out the final cycles of some instructions at the same time that it fetches the next i...
by ulfalizer
Tue Oct 08, 2013 6:41 am
Forum: NESemdev
Topic: First steps in writing an emulator
Replies: 75
Views: 29748

Re: First steps in writing an emulator

You can look in http://nesdev.com/6502_cpu.txt to see what reads/writes are done for different instructions. Implementing the instructions like in that doc is feasible, and makes the timing work out "automagically" without tables. You can also factor out the fetch of the opcode and the byte after t...
by ulfalizer
Mon Oct 07, 2013 3:48 pm
Forum: NESemdev
Topic: First steps in writing an emulator
Replies: 75
Views: 29748

Re: First steps in writing an emulator

For what it's worth, I do "slow" CPU emulation with interrupt polling in each instruction and no prediction Hmm, I was going to write a interrupt function that just sets the program counter whenever it's called. How did you set it up to check for interrupts every cycle? I would imagine that's how t...
by ulfalizer
Mon Oct 07, 2013 1:41 pm
Forum: NESemdev
Topic: SDL slowness while scrolling in Firefox on X11
Replies: 10
Views: 3893

Re: SDL slowness while scrolling in Firefox on X11

Firefox > Preferences > Preferences > Advanced > General > Browsing Turn OFF smooth scrolling, as I did several Firefox versions ago, and see if that fixes anything. I couldn't even find a smooth scrolling setting in Chromium, so I have a feeling that might be the reason for the difference. Might'v...
by ulfalizer
Mon Oct 07, 2013 9:29 am
Forum: NESemdev
Topic: First steps in writing an emulator
Replies: 75
Views: 29748

Re: First steps in writing an emulator

When it comes to inlining, one thing you should definitely do is whole-program/link-time optimization. When you're callings lots of function per tick, letting the compiler inline across compilation units can help a lot.
by ulfalizer
Mon Oct 07, 2013 9:16 am
Forum: NESemdev
Topic: First steps in writing an emulator
Replies: 75
Views: 29748

Re: First steps in writing an emulator

For what it's worth, I do "slow" CPU emulation with interrupt polling in each instruction and no prediction, and CPU emulation accounts for about 4-5% of the runtime in my emulator (out of a total of using about 40% of one core on my two-year-old Core-i7 2600K). Most of that is in the read() and wri...
by ulfalizer
Mon Oct 07, 2013 7:59 am
Forum: NESemdev
Topic: SDL slowness while scrolling in Firefox on X11
Replies: 10
Views: 3893

Re: SDL slowness while scrolling in Firefox on X11

Using software rendering doesn't help btw, so I'm guessing it's hitting a bottleneck in the 3D-accelerated desktop.
by ulfalizer
Mon Oct 07, 2013 7:49 am
Forum: NESemdev
Topic: SDL slowness while scrolling in Firefox on X11
Replies: 10
Views: 3893

SDL slowness while scrolling in Firefox on X11

Scrolling in Firefox in GNOME/Compiz (with at least the nouveau driver) makes SDL_Flip() and SDL_RenderPresent() (SDL2) extremely slow for me, to the point of only being able to do ~30 FPS with everything removed but those calls. Chromium doesn't cause nearly the same slowdown. Might be related to t...