nesdev.org

There seems to be a bit of confusion in the community as to what the practical uses are for the third nametable supported by MMC5 (in EXRAM mode 0). The example mirroring setups using 3 nametables on the wiki (both on the "Mirroring" page and the MMC5 page) are frankly of dubious practical...

I think using a NES 2.0 submapper for each combination of mapper and ADPCM chip that's verified to exist as real hardware makes more sense than adding entirely new header fields just for them. Whatever type of sound chip is used, its registers have to be mapped in a way that doesn't clash with mappe...

Are these ROMs separate chips mounted on the PCB or internal to the sound chip? If they're built into the chip, then the ROM size is implied by the type of chip (i.e. the mapper).

You need some way to distinguish between RAM and ROM. ROM shouldn't change when software writes to it through the PPU.

I'm now investigating the assembly language initialization/NMI/syscall code, or "BIOS" as Koei apparently called it . In the MMC5 games there appear to be three major versions of the BIOS: one used in Nobunaga's Ambition 2, Bandit Kings, Ishin no Arashi and Rot3K2 (with minor changes per g...

Why not look at and extract the 16bit KOEI titles to see if they already have the above in 16bit? Apparently their early SNES titles (e.g. Romance of the Three Kingdoms II) do use the same bytecode. Because the virtual machine has no support for an address space larger than 16 bits, they have to co...

The TIA implements the ÷15 as a series of carefully-tuned analog delays from the original NTSC colorburst frequency crystal. When it came to the PAL revision, they gave up retuning the inverters and only gave you 12 angles instead. It's much harder to move analog designs from one IC fabrication fac...

*edit* whoops, didn't realize tepples just posted. Hmm, I'm confused by something. Why doesn't writing to the bank select register just reset mmc3's internal state? In other words, say my main thread does this: ;write to bank select (for PRG) ; <<NMI INTERRUPTS HERE ;write to bank data and my nmi d...

MMC3 chr-ram boards needs the chr-ram bank to be set since the value at power-on is unknown. I had the same issue in hardware with my first mmc3 char-ram cart. The emulators sets the bank to 0 by default but this is not the case on the real thing. Well, I thought that this would be enough for me to...

On the NES, each palette entry of the 2 x 4 on-screen palettes takes one byte, i.e. each palette entry can have a value of 0-255. No, they can't. The PPU's internal palette RAM is only six bits wide. When you write to it, the upper bits are simply discarded--you can verify this by reading it back v...

I don't have a socketed original VRC4 board to test with. But I could test on one of my flash boards with the my replica VRC4 if that's of value. FWIW, it's logically equivalent to my knowledge displaying scanline counter artifacts identically to an original kid dracula cart. Sure, that's better th...

I would greatly appreciate it if someone could test the attached WIP on a real VRC4 board (any will do, but it must be VRC4 and not VRC2--the IRQs are what I'm interested in) I'm getting inconsistent IRQ timing between emulators. I think I know what the main cause is (accurately checking IRQs on the...

With the number of SNESes that seem to be suffering sudden CPU/PPU failure in recent years, encouraging a cartridge hot-swapping fad seems like the height of irresponsibility...

I'm experiencing some sort of color math emulation bug in bsnes-plus (accuracy version). I've tried this test ROM in several other emulators (no$sns, higan, snes9x, etc) and it looks correct. However, when running in bsnes-plus-accuracy the fog/clouds are displayed with a different random color on ...

Ahh I see, guess I misunderstood that looking back at my notes. Thanks for clearing that up. Something that might be of interest is to add detection of what's seen at $6000-7FFF. Whether it's VRC2 $6000-6FFF latch on bit 0, VRC4 2KByte RAM mirrored $6000-6FFF, or 8KB of PRG-RAM. I considered includ...