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Bizmuth 1.0.0 is available

November 1, 2026Bizmuth

Bizmuth 1.0.0 is available to download — the first release out of beta. The Next’s board is now a choice, its configuration flash is emulated, and the picture follows the VGA or HDMI connector. 40 fixes bring the Next closer to the hardware: its clock, the AY’s pitch and noise, and how the layers stack.

Breaking

  • Save states written by 1.0.0-rc3 or earlier no longer load. The format is v23; an older state is refused with a message naming its version.

Added

  • A choice of Next board — KS1 (issue 2) with 1 MB or 2 MB, KS2 (issue 4) or KS3 (issue 5) [--board, --ks1-ram, Preferences ▸ General]. A save state restores the board it was taken on.
  • The 32 MB configuration flash, loaded from an image file and written back to it [--flash, --flash-ro]. A guest reloading the FPGA stops the machine and reports the slot, in a headless capture, over ADP and to Rhai.
  • VGA or HDMI output [Preferences ▸ Display, --video-output]. At 60 Hz the window shows the 240 or 249 lines that connector shows.
  • File associations on macOS, Windows and Linux, as the default for .nex and .bzst. bizmuth FILE opens a program, tape, disk or save state by its extension, and a dropped .bzst restores it.
  • --rtc, --mem-wait and --im2-daisy turn on for one run what the config turns off.
  • ADP and MCP status, --version and the About box name the board and core.

Fixed

40 fixes, among them:

  • The Next ran 1.34% fast, and so did its AY, DAC and beeper pitch. Nextreg $11 video profiles 1–6 now run at their own clock.
  • Every AY tone played flat, and AY noise ran about an octave high.
  • A CTC interrupt in pulse mode held /INT until RETI, so a handler ending EI : RET ran once and never again.
  • Sprites were always drawn on top in wide Layer 2 and in the blend modes; nextreg $68’s blend source bits had no effect.
  • A .nex loaded without .nexload that called a 48K ROM routine ended in the NextZXOS menu.
  • A DMA CONTINUE repeated the last block, and an IM2 interrupt enabled in nextreg $CC or $CD let a DMA transfer run to the end instead of pausing it until RETI.

The full changelog has every change.

Bizmuth is free. Get it from the Downloads page, or try it in your browser. ROMs and SD images are user-supplied and not included.