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Bizmuth 1.0.0-beta2 is available

September 2, 2026Bizmuth beta

Bizmuth 1.0.0-beta2 is available to download — 174 changes since beta 1. Mostly correctness: 123 fixes, a lot of them hardware behaviour that had been quietly wrong on the classic machines.

Breaking

  • Save states from beta 1 won’t load. Format is v16; take a fresh one.
  • --wav/--wav-sources write WAVE files, not raw floats. Per-source files are now beeper.wav/ay.wav/dac.wav.
  • Breakpoint conditions read memory as mem[addr], not (addr). ( ) only groups now.
  • Script I/O handlers need watch_io, as memory ones have always needed watch_mem.

Added

  • ESP bridging and emulation — .http and .getit work with no extra hardware [--esp]
  • Source-level debugging: symbol names as arguments, file:line on every stop [--sld]
  • assert and debug in FantASM source become breakpoints; headless reports every failure
  • Serial fault injection — dropped bytes, overruns, framing errors, a silent far end [serial]
  • Mouse injection, live and scheduled [--mouse, ADP mouse, Rhai mouse()]
  • Breakpoint conditions: arithmetic, shifts, phys[], port[], widths, symbols
  • Scripts can read every port the CPU can, without disturbing it
  • Log to a file — the only way to capture one on Windows [--log-file]
  • Show/hide the toolbar [View ▸ Toolbar]
  • RTC fitted, and hide the status bar in full screen [Preferences]
  • Boot cap split out of the overloaded --auto-keys [--max-boot-frames]

Fixed

  • 17 nasty crash and hang bugs — malformed .dsk, .z80, TZX and SD images, a looping directory tree, a poisoned UI mutex that killed the whole window, out-of-range floppy commands
  • 24 debugger fixes — conditional breakpoints and bt() did nothing at all on the classic machines; breakpoints and symbols were lost on a machine switch; a paused ADP session hung DeZog
  • 14 timing and contention fixes — a +2A/+3 stalled 1 T-state in 8 where hardware stalls 7; memory above $BFFF ran untimed on the 128K/+2A/+3; the floating bus was 60 T-states out
  • 13 +3 floppy fixes — FORMAT TRACK didn’t format, multi-sector writes wrote one sector, a +2A answered floppy ports it hasn’t got
  • 12 UART fixes — wrong reset values, no flow control, no error bits, no transmit FIFO
  • 12 video fixes — Layer 2 banks ≥ $80 read the wrong 16K, 640×256 X-scroll moved 1px not 2, writes to the off-screen bank painted over the display
  • 11 interface fixes — Full Screen only maximised, Next Navigation had no menu item, Preferences tabs were clipped, the Wayland pointer wandered off-window
  • 6 tape fixes — the Next refused tapes outright; 6 TZX block types read as truncated
  • 6 paging and reset fixes — OUT ($0FFD),A repaged a +2A/+3; reset ejected the tape
  • 5 CLI/headless fixes — flags accepted and silently ignored on paths that never applied them
  • Plus: 128K .sna files of 147487 bytes load, the CTC vector is taken only from channel 0, and nextreg $11 reads back what the hardware reports

The full changelog has the rest.

Bizmuth is free, and still in beta. Get it from the Downloads page — there are now Windows installer and Arch packages alongside the existing builds. ROMs and SD images are user-supplied and not included.