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4 / 20-03-2020





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This is a new multi-system emulator, which shares emulation cores with higan and is foremost focused on accuracy. With that in mind, byuu aims to be much more user friendly than higan (think of byuu as easy mode, and higan as advanced mode).

The goal of byuu is to carry forward the breakout success of bsnes for all of higan's emulation cores, and not just for the SNES alone. bsnes, by being much easier to use, led to a resurgence in support that resulted in several new features, speed optimizations, bug reports, and emulator accuracy improvements. I hope to rekindle the same interest in all 25 of my supported emulation cores with this new emulator.


Most Recent Changes

This release substantially improves PC Engine emulation, fixing 80% of known issues.

Regretfully, this will be my final release. I will be stepping down, and my emulators will be maintained going forward as a team project. I'll have more to say on this in the near future in a separate post.


  • PC Engine: improved IRQ handling significantly

  • PC Engine: fixed T-flag instructions, and implemented all addressing modes for it

  • PC Engine: improved VDP penalty cycle timing

  • PC Engine: always fire Vblank IRQs every frame, regardless of VDW setting

  • PC Engine: add support for STreet Fighter II CE's custom mapper

  • PC Engine: emulated MPR latch used by TMA and TAM instructions

  • PC Engine: randomize various registers and memory at power-on

  • PC Engine: do not allow block moves to read from $ff:0800-17ff

  • PC Engine: always set P.B flag (except when pushing P during BRK)

  • PC Engine: delay PSG synchronization when not needed (~8% speedup for accuracy profile)

  • PC Engine: emulate 4-color background and sprite modes

  • PC Engine: emulate grayscale VCE mode

  • PC Engine: emulate extra scanline VCE mode

  • PC Engine: fixed VRAM->VRAM DMA transfers (was transferring one byte less than it should)

  • PC Engine: improve burst-mode emulation (early VRAM->VRAM termination, etc)

  • PC Engine: add display timing latching to the performance profile's scanline renderer

  • PC Engine: many disassembler improvements

  • PC Engine CD: added skeleton implementation (non-functional)

  • Mega Drive: fix a crash when loading Sonic & Knuckles or the Game Genie without a daughter cartridge connected

  • icarus: fix typo in save RAM portion of Master System game manifests (was marked as ROM by mistake)

  • byuu: don't show the program icon briefly when loading a new game

  • byuu: focus the viewport after loading games

  • byuu: add trace log path override option

  • byuu: use save path override for SNES save RAM files as well

Show Previous Changes

On their next update, this section will be refreshed.

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