RP's cockpit displays decoded near-empty (top-strip only, a copy off-screen at
VRAM 0x100000) while BT's were full. Root cause was NOT the VDB decode (byte
split/palettes/stride all correct, proven by BT) but an SVGA bank-switch
GRANULARITY mismatch: RP's REL410/RP/GAUGE/L4GAUGE.INI [640x480x16] used
granularityInKB=4 vs BT's 64 on the same STB Horizon+ (CL-GD5434). DOSBox-X's
CL-GD5434 bank emulation handles 64KB granularity (BT full) but mishandles the
4KB-granular paged gauge writes, scattering them off-screen.
FIX (config, no rebuild): RP L4GAUGE.INI granularityInKB 4->64 (matches BT,
same card). VERIFIED live: VRAM content scan went from 0x0+0x100000 (top-strip
+ off-screen) to the FULL framebuffer 0x0..0x90000 populated; radar +
upper-center MFD confirmed correct, rest under reference check.
Also commits the VDB diagnostic tooling that found it (vpxlog.cpp, all
default-off): VDB_SCAN (VRAM content locator -- decisive), VDB_PALDUMP,
pixel-mask value logging, VDB_REALSTRIDE + live mode/stride/start logging,
VDB_BASE read-base override, VDB_APPLYMASK DAC-mask honoring. Full writeup in
VDB-NOTES.md.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
CydandClaude Fable 5
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