ATARI 8 bit emulator

Posted Fri Mar 29, 2013 9:50 AM

Happy Easter,

a new release of Atari++, the portable atari emulator for Linux and windows has been released here in the download section - as usual, you find there the Linux sources and a compiled version for 32-bit Windows. Release 1.72 fixes a couple of nasty little bugs that were overlooked, but the main new feature is the support of ATX images, plus many small changes to Os++, the included operating system for the 8-bits.

  • The binary file loader automatically generated when inserting a COM or EXE into the disk drive and booting from it is now much shorter and requires a lot less RAM. It requires now, however, an additional ESCape code and hence emulator support. This will now also load binary files that require RAM from 0x800 and up.
  • This release adds support for ATX files and includes an emulation of the disk drive timing, handling of bad and duplicate sectors and a more precise emulation of the SIO timing.
  • An additional type of watch point was added: The default watch point now only reacts on memory writes, whereas the new watch point continues to react on reads and writes.
  • Experimented a lot with the timing of the GTIA Prior writing and found that the currently implemented logic is actually very close to the real system, additional delay cycles make results only worse, not better. Thus, leaving it as it is right now.
  • The SDL StringGadget now reacts on Ctrl+Backspace and Ctrl+Delete and erases its contents on this keyboard command.
  • Added emulation for "stuck" Player/Missile shift registers when switching from 4x or 2x expansion to the size register "2" value, which is almost, but not quite 1x expansion.
  • The built-in Os blocks NMIs now early in the reset cycle and by that tries to work around bad display lists left over by buggy programs.
  • Minor modification in the built-in FMS (Dos 2.++): CONFIG.SYS can now change the position of the FMS buffers by poking into DiskBufferBase $710,$711 and relocate them.
  • Minor modification of the short VBI: GPrior, ColBK and Col1 are now only reloaded if the graphics mode really requires it. This applies to fine scrolling text modes, and the text window modes with the GTIA modes (modes 9+64,10+64 and 11+64). This fixes compatibility issues with Atari Tennis and some Lucasfilms intros.
  • Minor modifications in the FMS: Rename with wildcard was broken, and the FMS no longer tries to load non-valid VTOCs.
  • The DUP COPY command avoids now trying to overwrite BASIC program memory or other user memory protected correctly by setting APPMEMHI. Some cartridges do not set this Os pointer correctly, though. Mac/65 does not. The new DUP command NEW will erase user memory and make it available for COPY.
  • Fixed a long standing bug of all Dos 2.XX compatible FMS'es: Directory reading mode did not cooperate with any other operations that would access the directory, and would invalidate the directory access channel. This is no longer the case now. Additionally, reading the directory sets now the EOF warning flag (Y = 3) correctly right before the EOF.
  • The STATUS command, as specified by DOS 2.0S and DOS 2.5, was actually quite unuseful as it required a file specification which was never supplied by BASIC. The new implementation returns the status of the last CIO command on the same channel if the channel is open, allowing BASIC for example to access the near-EOF warning return code.

Anti-News: (or, what does not yet work):
  • Antic DMACtrl in-line adjustment tricks are not supported, neither any HScroll adjustments to disable the DMA-stop.
  • Bus noise picked up by GTIA if GRACTL is enabled but DMACTL is disabled is currently not emulated correctly.
  • Bus noise picked up by ANTIC on the right side of wide playfield screens is currently not emulated at all (and neither visible if it would).
  • The POKEY soft-reset cylce is currently not emulated completely.
  • Bit-banging serial output is currently not emulated at all.

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