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CydandClaude Opus 4.8 47fe174c6e Add VDB (VWE LBE4 video splitter) device + fault disassembly findings

The VDB is the ISA card that fans the PC's Cirrus Logic framebuffer to the six
secondary cockpit displays (5 mono + 1 color), dividing the pixel clock. From
the driver (CODE/RP/MUNGA_L4/L4SVGA16.ASM, L4VB16.CPP; "Adam's port decoder
design" -- Adam G., VWE hardware):
  0x300/0x308/0x310  three VGA-DAC-style palette groups
  0x31A / 0x319      splitter high-color clock divider ON / OFF

New emulated VDB device in vpxlog.cpp at I/O 0x300-0x31A (active when logging,
disable with VDB=0): decodes palette write-address/data/mask/read-address and
the clock strobes, recording palette contents + splitter state so the six-
display encoding can be decoded later. Validated: with gauges enabled
(gauge.conf, setenv arg4=g) the game issues "splitter clock ON (0x31A)" ->
captured. The board is write-only (game never reads it, per driver + owner),
so its absence is not the crash.

Crash diagnosis (BTL4OPT.EXE CODE+0x123B): the faulting routine is a heap
free() with boundary-tag coalescing; it was handed a garbage block pointer
(value 2). Symptom of upstream corruption, reached only when the RIO is in
sync and the sim advances. HISTORY.md gains a "Cockpit display hardware -- the
VDB" section with the attribution.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

2026-07-03 15:55:00 -05:00

README.md

Phase 1 complete: captured VPX boot conversation from shipped binary

2026-07-02 22:46:20 -05:00

vpxlog.cpp

Add VDB (VWE LBE4 video splitter) device + fault disassembly findings

2026-07-03 15:55:00 -05:00

README.md

VPX device — DOSBox-X integration

Our original source for the emulated Division VPX link adapter. Kept here under version control because the DOSBox-X source tree itself (emulator/src/, ~490 MB) is git-ignored.

vpxlog.cpp — Phase 1 logging device. Impersonates the INMOS C012 link adapter at I/O base 0x150, answers status reads so the game keeps transmitting, and logs every access to $VPXLOG. (Phase 2 will grow this into a responding transputer-monitor + i860-loader + frame-stream renderer, or fork into a separate vpx.cpp.)

Applying to a DOSBox-X source checkout

Tested against DOSBox-X v2026.06.02, MSYS2 mingw64.

Copy the device in:

cp emulator/vpx-device/vpxlog.cpp  emulator/src/src/hardware/vpxlog.cpp

Add it to the hardware build — in src/src/hardware/Makefile.am, append vpxlog.cpp to libhardware_a_SOURCES (we inserted it after glide.cpp).
Call the init — in src/src/gui/sdlmain.cpp, declare void VPXLOG_Init(); next to the other *_Init() prototypes and call VPXLOG_Init(); right after GLIDE_Init(); in the machine bring-up sequence.

Build:

cd emulator/src
./build-mingw-sdl2 --enable-debug=heavy

Output: src/src/dosbox-x.exe.

Running

set VPXLOG=C:\VWE\TeslaRel410\emulator\vpxlog.txt
emulator\src\src\dosbox-x.exe -conf emulator\capture.conf
python emulator\analyze_capture.py

With VPXLOG unset the device is inert and the build behaves like stock DOSBox-X.