nesdev.org

That's not so much treating everything as volatile, as not doing any CSE whatsoever.

The general use of (L)GPL code with commercial games hit one of these four categories: GPL engine/code, proprietary data. -- Essentially what the old idTech engines do now. Proprietary engine and data, dynamically linked with LGPL support libraries. This is what Loki did to release games on linux us...

Remember that the license has absolutely nothing to do with what you yourself can do with the code. That said, the usual sort that'd try to exploit something commercially without asking are also the sort that you probably don't have the time, resources, or ability to bring to task for it -- hong kon...

You also have to check those locations + 512, as some copiers stuck a 512 byte header on the front. Theoretically the file extension would tell you about that, but they're generally unreliable.

Yes. You store the current portamento offset, and add speed to it every frame (or every N frames, etc). A speed of 1, added every frame, will smoothly (or as smoothly as is possible) slide up one semitone in just over 4 seconds (256 steps between semitones, 1 step per frame, 60 Hz). If you want mult...

In a bit more detail... With no pitch bending, notes are pretty easily specified as a number of semitones above some base. A number of games use the MIDI note range, which is 128 tones, ranging from C-1 to somewhere around C10. The usable range on the NES is a little smaller than that, ranging from ...

One way to do it is to treat your notes as 8.8 fixed point, whole choosing a semitone, fraction the distance to the next, and instead of a table, just doing the lerp math. Yeah, the multiply sucks donkey balls as far as cycles go, but it can be done without huge tables, and IIRC you can shortcut a b...

Software Configurable != Unlimited

Most VGA cards had software configurable DACs too, but at some point you run into the limits of the dot clock range or memory bandwidth avaliable

If you moved the y/ptr increment around a bit, you could avoid the need for the bit or the asl, as lda will set the N flag appropriately.

After looking at it, albeit briefly, a couple things come to mind: Column transposing is going to be rather slow, or need an excessively large LUT. It's probably better for the group header to have the bits stored chunky rather than planar, as it cuts down on the amount of RMW rotates needed. The co...

interfacing to an actual cart complicates the hell out of things, as most fpgas aren't 5V tolerant. It's a hell of a lot easier to keep everything in nice modern low voltage stuff.

The serial bug is actually trivial to do with a real 6502. The DMC dma just pulls RDY down for 4 cycles, and does it's write on the 4th. The CPU ignores RDY for writes, for reads, it holds the address lines stable, and pauses internal operations (this'd be for adding wait states, for instance) If DM...

Coming from the old school PC gamedev side of things, free info is for whatever use someone can make of it. For ice, it's been done a number of ways. The usual NES approach has been something like what you described, where jumping could kill your forward momentum, landing while moving would keep you...

Or it's just a synchronous up/down counter with an asynch load. I'd guess it's something like this: module dmc_counter(clk, ena, dir, load, d, q); input clk, ena, dir, load; input [7:0] d; output reg [7:0] q; always @(posedge clk) if (load) q <= d; else if (ena) else if (dir) q <= q + 1'b1; else q <...

I believe the "cash discount" approach in the US tends to get retailers in trouble with Visa/MC as it's a violation of the merchant agreement.