nesdev.org

Has Stars SE Demo (PD) been developed (or tested afterwards) on a real NES ? APU docs say frame IRQs are enabled on boot, but if I do this in my emulator, that demo will just hang with a black screen. If I don't enable frame IRQs on boot, it will work.

1: Simple question first. After writing to 0x4010 (or 0x400e for that matter), will the next action start rightaway, or will it wait a few cycles, specified in the lsb's, before doing the next action ? 2: Let's say that a sprite DMA transfer starts at (relative) CPU cycle 0, and it ends at cycle 512...

This is confirmed to happen on the real hardware - modifications to the fine X-scroll value (bottom 3 bits of first write to $2005) take effect immediately while coarse scroll (upper 5 bits of first write to $2005) are only applied at the beginning of each scanline. That's a pity, in a way. It also...

Could anyone test this on a real NES, to confirm the glitchy behaviour ? I've tested these glitches with several emulators. Perhaps others could post specific game glitches that look like emulator glitches too. 1: Rad Racer: when you go off the road, some scanlines will shift, causing parts of the r...

R-Y: 112° ´ 0.83, G-Y: 252° ´ 0.3 (B-Y: 0° ´ 1) This would translate into the following decoder matrix: R = Y + 1.539*V - 0.622*U G = Y - 0.571*V - 0.185*U B = Y + 0.000*V + 2.000*U How did you get those values from those angles ? When I don't understand something, I just do trial-and-error, and th...

Not only Dragon Quest is using it. In my emulator, these games had problems before emulation of frame IRQ's, and are working fine now:

Qix: locked up when starting a game
Door Door: locked up when dying
Shin 4 Nin Uchi Mahjong: locked up at the title screen

Well, NMI's occur every (262*341)/3=~29781 CPU cycles, so if you'd reset the frame sequencer, and enable frame IRQ's right at the start of the NMI handler by writing 0 to 0x4017, the frame IRQ would never happen, since it would start counting down again from 29830, and never reach zero. Right ?

About the frame sequencer: I won't blame anyone on errors, since this post is quite old: http://nesdev.com/cgi-bin/wwwthreads/showpost.pl?Board=newbie&Number=1171&page=&view=&mode=threaded&sb=#Post1171 "Assuming $4017 is written with $00 at the beginning of the VBL handler. ...

The NES cpu runs at (236250000/11)/12 hz, that is 1789772.7272727272hz. NTSC refresh rate is 60/1.001 hz, that is 59.94005994005994005994005994005994hz. 3 PPU cycles take 1 CPU cycle, there are 341 PPU cycles in one scanline, and 262 scanlines in one frame. Now, if I calculate the NES cpu speed, bas...

Hmm, it updates the ppu address mid-scanline. I was filling the background scanline buffer using the x tile offset from the ppu address, and that's why this demo didn't look messy in my emulator. But, it's plain wrong handling it that way, so I've fixed it and it looks alright now (meaning: lots of ...

http://nesdev.com/Stretch.zip

What causes emulators to show garbage inside and to the right of the wave ?
... cause mine doesn't, it shows black lines instead, and I think that's a bad thing :p

There's a game where you can test that behaviour. I think it's one of the Megaman games, where you have to jump over the powerbar. Sorry I don't remember the details, but I'm sure someone else does.

I've implemented this feature in an emulator of mine, not NES though. And I must say that the result is indeed awesome. Before implementing it, I thought it would be an unnecessary feature, but I've changed my mind now. It's very handy (and cool ;p ) to use it, especially in action games where you'd...

Why not let the iNES header battery bit decide whether you enable SRAM or not ? I mean for mappers that normally don't use WRAM. Jagasian: rewinding like in Prince of Persia would be very cool indeed, but I think the NES is too complex for that to implement easily. An array of savestates made each s...

Yeah, Death Race relies on the 'feature' that dataline 0 on the ROM always wins when writing to the mapper. It boots fine here after implementing that just now (thanks for the link)... something like: written_data|=(read_rom(address)&1);