DOS ain't dead - DarkDebugger

DarkDebugger (Users)

posted by Japheth , Germany (South), 23.06.2022, 17:05

I'm currently checking an old graphics app in a vga 16-color mode. This app used to work, but on newer cards the output is "scattered" ( or perhaps it's not the "newer cards", but the "newer cpus").

As it has turned out, I had to make this change:

; mov al,ah ; xchg al,[bx] mov al,[bx] mov [bx],ah

Using XCHG with memory operands is usually a bad idea, but even more so in the vga "plane" modes. Better do a clean read to fill the "latch" register, then the write. I guess it's also "significantly" faster.

---
MS-DOS forever!

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Complete thread:

JEMM386 v5.81 hangs - CandyMan, 03.05.2022, 23:23
- JEMM386 v5.81 hangs - Japheth, 04.05.2022, 03:18
  - JEMM386 v5.81 hangs - CandyMan, 04.05.2022, 09:30
    - JEMM386 v5.81 hangs - Japheth, 04.05.2022, 10:34
      - JEMM386 v5.81 hangs - CandyMan, 04.05.2022, 16:02
        JEMM386 v5.81 hangs - Japheth, 05.05.2022, 08:11
        JEMM386 v5.81 hangs - RayeR, 18.05.2022, 22:48
        JEMM386 v5.81 hangs - CandyMan, 23.05.2022, 17:43
        DarkDebugger - RayeR, 25.05.2022, 17:59
        JEMM386 v5.81 hangs - CandyMan, 25.05.2022, 18:55
        DarkDebugger - RayeR, 26.05.2022, 03:59
        DarkDebugger - CandyMan, 26.05.2022, 19:41
        DarkDebugger - RayeR, 11.06.2022, 03:26
        DarkDebugger - CandyMan, 12.06.2022, 19:00
        DarkDebugger - RayeR, 17.06.2022, 19:09
        DarkDebugger - CandyMan, 18.06.2022, 22:41
        DarkDebugger - RayeR, 23.06.2022, 00:07
        DarkDebugger - CandyMan, 23.06.2022, 11:27
        DarkDebugger - Japheth, 23.06.2022, 17:05
      - JEMM386 v5.81 hangs - tkchia, 04.05.2022, 23:11
        JEMM386 v5.81 hangs - Japheth, 05.05.2022, 08:42
        JEMM386 v5.81 hangs - tkchia, 05.05.2022, 11:56
- JEMM386 v5.81 hangs - CandyMan, 25.05.2022, 18:59
  - JEMM386 v5.81 hangs - Japheth, 27.05.2022, 17:10
    - JEMM386 v5.81 hangs - CandyMan, 28.05.2022, 19:27
      - JEMM386 v5.81 hangs - Japheth, 29.05.2022, 04:46