A/NES 1.25 boosts Amiga NES emulation with speed-focused fixes

A/NES 1.25 landed on Aminet on July 13 as a rare NES emulator update aimed squarely at classic Amiga hardware, not at modern convenience. The package is written in 100% 680x0 assembler, needs at least a 68020 CPU, and still asks for an AGA chipset plus 2 to 4 MB of FastRAM, with 68040 and 68060 machines strongly recommended.

That hardware focus is what makes the new release matter. Aminet describes A/NES as the only NES and Famicom emulator still in development for Classic AmigaOS, and v1.25 keeps that effort centered on the parts that decide whether a game feels playable on real machines: keyboard response, interrupt handling, graphics routines, and mapper timing. Morgan uploaded the package, which keeps the project in the same hands that have been pushing it through a short burst of maintenance this spring and summer.

The practical gain in 1.25 is not a flashy feature list. Faster keyboard routines cut the cost of input handling, which can make directions and button presses feel more immediate on slower Amigas. Interrupt handling was also reworked to reduce overhead and leave more room for the main emulator loop, a small change that can matter a lot when one old computer is trying to impersonate another old computer cycle by cycle.

The most useful option is the ability to disable MMC3 IRQ handling on slower systems. MMC3 is one of Nintendo’s major mapper ASICs, and NESdev’s documentation shows why it is so important: the chip’s scanline IRQs and fine-grained PRG and CHR bankswitching drive split-screen status bars, raster effects, and other tricks that many games rely on. Turning that handling off can buy smoother performance on a sluggish Amiga, but it is not a universal speed hack. Some games will display incorrectly if the IRQs are disabled, so the setting works as a tradeoff rather than a blanket fix.

That approach fits the rest of A/NES’ recent history. Version 1.24, released June 19, added a new audio engine, fixed sprite 0 hit detection, sped up MMC4 CHR-bankswapping, and added NTSC and PAL ROM support. Version 1.23 had already rewritten the startup and interrupt handler, fixed an MMC3 IRQ bug, and added performance optimizations. Put together, the releases show a project shaving overhead where it counts, and 1.25 pushes that work a little further for anyone still asking a classic Amiga to run NES games as cleanly as possible.