ZEsarUX:known bugs

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You may want also to check the official ZEsarUX FAQ to see if you have a known issue which has solution (ZX Next is "TBBlue" type of machine).

Version 10.2:

  • missing Nextreg $64 "video line offset" (core 3.1.5)
  • blending modes are not implemented
  • DMA: too many differences to list, but most crucial: slow "burst" functionality is missing, CONTINUE is not supported, legacy Z80 mode is not implemented, all transfers are "instant", dmaDebug.sna test does "reset" machine after ENABLE command (didn't look what exactly is broken about the last one)
  • ULA (bank 4/7, timex hires/hicol) scroll doesn't scroll per pixel on X-axis, but per 8px (char)
  • ULA (bank 4/7, timex hires/hicol) half-width scroll is not implemented
  • ULA (bank 4/7, timex hires/hicol) clipping on Y-axis scrolls too (should not)
  • relative sprites don't wrap correctly around 512x512 coordinate space in extreme cases (8x scale and some positions)
  • sprites rendering is not one-scanline-buffer delayed and all changes in sprites affect current scanline
  • NextRegs $09 reads wrong values, NextReg $02 soft reset doesn't work same as HW
  • audio has "clicks" and noise on many platforms, although YMMV
  • modifications to NextRegs done in copper propagate to rendering usually only once per scanline, usually retroactively for full scanline when triggered in h-blank area (palette changes, X/Y offsets, etc)
  • when running without the full NextZXOS card image, the esxdos services are provided by the emulator itself, which does not implement all of them, and they don't always return the state described by the NextZXOS documentation
  • missing all(?) features/changes of cores after version 3.1.5 (the emulator itself reports as core 3.1.11, but I haven't find any functionality related to the changes in real cores)
  • Z80: EI instruction, FD and DD prefix don't inhibit accepting masked interrupt until next instruction is executed (or postpone interrupt request until some instruction which allows it, and then handle interrupt, even if /INT signal is gone)
  • Z80: extra IX/IY prefix is wrongly processed and with even number of prefixes the next instruction is using HL instead of IX/IY
  • Z80: (should not affect any ZX SW, just emulation accuracy) ccf/scf doesn't produce stable outcome in undocumented flags

Untested since 10.2 (may be already fixed, probably not):

  • ULA+tilemode does not support stencil mode, and transparency fallback color is not used in some edge cases (disabled ULA + clipped tiles)
  • tilemode doesn't wrap in memory the same way as HW (when gfx/map address is toward end of Bank 5)
  • direct loading of NEX file doesn't init the machine in the same way as NEXLOAD from NextZXOS (it's close, but few things are different)
  • should be fixed, untested in linux trying to open "Debug CPU" window will smash the stack and crash the emulator, you can work around it by using "-fno-stack-protector" during compilation to continue running even with damaged stack content.

Fixed since 10.2 final:

  • sprite rendering-priority (b6 in NextReg $15) is not implemented
  • Z80: (should not affect any ZX SW, just emulation accuracy) block instruction flags while repeating are incorrect

Other Issues (not a bug):

  • 28MHz mode requires quite powerful PC to emulate it smoothly, "lagging" emulator menu/etc is likely to happen in 28MHz mode and unfit for many development purposes.
  • don't use "--enable-esxdos-handler" option together with running NextZXOS from full MMC card image - it will clash with the MMC functionality