nesdev.org

You should not rely on the state of anything at powerup and reset. I/O register contents and WRAM/VRAM/CGRAM contents can potentially be anything at power-on, and generally keep their values across resets. In addition, if someone is using a flashcart to run your ROM on the real console, the flashcar...

Page 2 of this interview explains that Ricoh was the only company with the necessary manufacturing capacity available at the time, due to PCs getting big in Japan. It also mentions that it was Ricoh's engineers who apparently recommended the 6502, though it doesn't go into much detail as to why.

An important distinction here, which I'm not sure if you're aware of, is the difference between master cycles and CPU cycles . The numbers you've been talking about are master cycles, not CPU cycles. For NTSC, these cycles run on a ~21.477 MHz clock. However, CPU cycles are different. Depending on t...

Your ROM file does seem fine, though the header claims the ROM is 256 KB when it's actually 32 KB, and the checksums haven't been set. My guess is that the ROM size is the problem, and it should be zero-padded out to 256 KB. I don't own a SD2SNES, but at least on the Super EverDrive, I've had proble...

You forgot a # before JOYH_LEFT and JOYH_RIGHT.

at whatever part of the file maps to $00FFB0-$00FFDF. That is one of the tricky parts, though, because unless you know ahead of time what that mapping is (e.g. known ROM hashes), you can't figure out that mapping without doing some guesswork. This involves judging whether the data at file offset 0x...

nicklausw wrote:changing the ROM type in the header from $30 to $20 (you had it set to HiROM, I believe?)

Nah, $30 means fast LoROM, versus $20 for slow LoROM (whereas HiROM is $21 or $31). Having $30 there shouldn't be an issue.

The color #$001f is in fact red, not green, and that's what's being written, so it sounds like it's actually working in that case.

Another problem I see is that you use jsr to call your init code, but that's where you set up the stack, so rts won't return you back where you were, because the stack pointer is no longer pointing at the address you need to return to. You should probably jmp to the init code, and jmp back instead. ...

I notice that your init code already turns off forced blanking. That might be interfering with your writes to $2122, since they're probably not happening during Vblank/Hblank.

What they mean is, autoreading doesn't start until a little bit after vblank, so HVBJOY can show up as "ready" from the previous frame before it becomes "not ready". It's better to wait for it to not be ready, and then wait for it to be ready, to make sure you don't end up readin...

Hang on, you have the software for the Emulator SE? Last I heard, people haven't been able to find that anywhere; is there a chance you could upload it somewhere?

I remember hearing something along the lines of Nintendo actually patching this stuff at run-time, rather than modifying the actual game images themselves. There's already evidence they've done stuff like this with the Virtual Console in things like EarthBound, which mitigates certain screen-flashin...

It seems HuCards (the cartridge format for the PC Engine) generally ranged from 256 KB to 1 MB. Apparently there was only a single PC Engine game on HuCard larger than 1 MB, namely Street Fighter II' clocking in at 2.5 MB. As for writing slow code, it depends. Of course there are things that, for in...

So, the main issue here is that the CPU and APU don't run at the same rate at all; they don't even use the same clock . For NTSC, everything with the CPU and PPU is based on master cycles with a rate of 21.44727 MHz. So, for instance, a fast CPU cycle is six master cycles (~3.58 MHz), and it takes t...