nesdev.org

One practical problem with fusemap recompilation as a web service is that obtaining synthesis software for old Xilinx FPGAs, such as the one in the PowerPak, is a pain. For FPGAs, that's likely true, and I don't know what if anything can be done about that unfortunate situation. CPLD fusemaps tend ...

The NES was designed with a pretty versatile cartridge slot, and during the life of the console people designed not only software for the machine, but a multitude of hardware improvements to go along with the games as well. Mapper design has the potential to be pretty fun, provided you know what yo...

Sometimes people try to solve a technical problem with the NES using a custom mapper. The problem often takes this form: NES is just barely too weak for the application. Super NES is too strong, and players would expect production values that a solo or duo can't deliver on time and on a ramen budge...

A significant number of Famiclones don't let you disable NTRAM. Is there a reliable way to test for these in software? Would it work, say, to write different values to $2000, $2400, $2800, and $2C00, and then try to read them all back? And if so, is there a reliable way to display a message if both...

For how to call a function through a function pointer, see Jump table and RTS Trick in the wiki. If you can afford dedicating 3 bytes of RAM to a springboard, and have fewer than 86 jump targets, have a page-aligned table of JMP instructions to each target, and a region of RAM that always holds $4C...

There's a similar edge case in how arithmetic shift right on a signed number is For a signed arithmetic shift right you can detect sign and correct the rounding with an ADC #0. A pseudo operation for signed divide by two might look like: CMP #$80 ; move sign into carry ADC #0 ; +1 if signed CMP #$8...

The only problem is that the JSON standard only allows decimal numbers, so hexadecimal numbers are off-limits. Many aspects of the design of Javascript are really terrible, but one very useful aspect of that language is that almost any modern system will have an implementation available which can b...

Oops. I really should have read that wiki more carefully myself! I was under the impression that you could actually control the phase of this timer by starting a new sample at some variable point in the NMI. But yes it does appear this was misunderstanding of mine. To be honest I ever only tried th...

I sort of struggle to see what MMC2 / MMC4 would provide that a scanline IRQ couldn't, except for a modest amount of saved CPU cycles. Using a scanline IRQ would require a relatively complex mapper chip. While MMC2/MMC4 are somewhat fancy, a game designed for MMC2 could be readily adapted for a dis...

I sort of struggle to see what MMC2 / MMC4 would provide that a scanline IRQ couldn't, except for a modest amount of saved CPU cycles. Using a scanline IRQ would require a relatively complex mapper chip. While MMC2/MMC4 are somewhat fancy, a game designed for MMC2 could be readily adapted for a dis...

As far as I know it, on the C64, there are registers for a fine scroll of only 0..7, after which point games normally have to manually shift the entire screen data by 1 column. Home computers (/ old IBM PCs) that didn't have any fine scrolling regs in hardware had to manually shift the entire scree...

The other big limitation of the NES is memory. It has only 2KB of RAM, which has to be used for anything that's dynamic (static content can be streamed directly from ROM in most cases). Games that must keep a lot of state for long periods can be difficult or even impossible to code. The size of des...

I appreciate the responses about mapping emulation, and would like to continue them soon in on another thread on the emulation forum, but my main purpose in asking whether any research had been done was to avoid duplicating any existing efforts in sketching out a proposal. My goal isn't to recreate ...

I think you perhaps misunderstood my intention. i wasn't intending circuit-level emulation, but rather a VM with an instruction set focused on bit manipulation and 2/4/8-way branching. No, I think I understood what you meant. It's still not for anyone. It's still a solution in search of a problem. ...

What, if any, research has been done with regard to designing a "universal mapper" emulation VM? I don't think it's a good idea./quote] I think you perhaps misunderstood my intention. i wasn't intending circuit-level emulation, but rather a VM with an instruction set focused on bit manipu...