3f23e2b98f
The internal noise shift register in this file uses a bit-reversed layout vs the canonical nesdev wiki model: output is read from bit 14 (not bit 0), the feedback taps are at 13/14 in long mode and 8/14 in short mode (mirrors of 0/1 and 0/6), and the register shifts left rather than right. The algorithm is algebraically equivalent to the wiki form, but the power-on state has to be mirrored as well. Real hardware initialises the LFSR to $0001 with bit 0 set. Under this file's mirroring, the equivalent state has bit 14 set - i.e. nreg = 0x4000, not nreg = 1. Starting at 1 placed the LFSR 14 steps off-phase from real hardware in long mode and at an entirely different position in the 93-cycle short-mode loop. Reported by NSFPlay author Brad Smith (rainwarrior) comparing moon8.nes audio against Mesen. Reproduced via headless libretro harness with per-channel solo bisection against negativeExponent's fceumm_next branch (which uses the un-mirrored nesdev layout): channel RMS diff vs _next (noise solo, 22-60s window) ------- ---------------------------------------------- square1 1 ( 0.4%) - bit-identical square2 1 ( 0.4%) - bit-identical triangle 178 (14.0%) - minor difference noise 1914 (125.8%) - completely off dmc 2 ( 0.4%) - bit-identical After this patch the noise-solo RMS drops to 6 (0.4%), bringing the noise channel into bit-exact agreement with _next/Mesen/NSFPlay. Full-mix moon8 audio RMS vs _next falls from 1135 to 126 across the 60-second test.
FCE Ultra mappers modified
FCEU "mappers modified" is an unofficial build of FCEU Ultra by CaH4e3, which supports a lot of new mappers including some obscure mappers such as one for unlicensed NES ROM's.
Sequential targets Light Guns support added
Support for Sequential targets Light Guns has been added. "Gun Aux A" serves as light sensor logic input.