The garbled top-strip render was a paging bug, not the video mode. The
pageFcnPtr in L4GAUGE.INI (C000:2616) is a red herring -- the driver's direct-
pointer path is commented out ("THIS DOES NOT WORK"); it pages via portable
VESA int 10h/4F05, which our S3 handles.
Real cause: window granularity. SVGASetPage passes the bank in granularity
units; the blit advances by pageDelta = pageSize/granularity per 64KB window
crossed. The INI's granularityInKB=4 is the Cirrus CL-GD5434's 4KB window
granularity (the pod's actual video card; the "STB Horizon+" board was
Cirrus-based). Our emulated S3 uses 64KB banks, so pageDelta=16 -> every bank
landed 16x too far -> the smear.
Fix (config only): L4GAUGE.INI [640x480x16] granularityInKB=64 (=sizeInKB, so
pageDelta=1, matching the S3's 64KB banks). Full framebuffer now pages
correctly -- 315+ frames, VDB splitter stays ON, display renders as expected
(blank between missions; user confirmed "that is the screen I expect").
ALPHA_1 is git-ignored so the INI edit isn't committed; reproduction + backup
(L4GAUGE.INI.orig) documented in GAUGE-NOTES.md.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Enabling gauges crashed (null-this, illegal 0x478). Root cause was NOT video:
the MUNGA main heap (fixed 6MB default) exhausted loading gauge images. The
heap size comes from getenv("HEAPSIZE") (BTL4OPT.EXE @0x401076; default
0x600000); the pod's PARAMETR.BAT sets it (:POD=15MB, :REVIEW/:LOOP=32MB) but
our minimal setenv launch never did. memsize is irrelevant (it's the game's
own heap, not DOS memory -- verified memsize=127 still gave 6MB). Pods have
32MB RAM so 15MB fits.
Fix (no binary patch): set HEAPSIZE=15000000 + L4GAUGE=640x480x16 in
gauge.conf. Game now runs sustained with gauges on (500+ frames); the VESA
640x480x16 mode switches fine on our emulated S3 and the cockpit instrument
panels draw (DISPLAY/PROGRAM/ENG DATA/TRIGGER CONFIG...).
patch_btl4opt.py also gained Verify_Failed (DEBUG-build assertion) neutral-
ization -- release-equivalent robustness, separate from the heap fix.
Known-open (GAUGE-NOTES.md): the framebuffer renders only a top strip,
garbled -- the game bank-switches via a hardcoded far pointer in L4GAUGE.INI
(C000:2616, the STB Horizon+ card's VESA WinFuncPtr) that isn't valid on our
emulated S3, so only the first bank(s) page in. Fixing bank-switching (or an
LFB mode) is next; then the full buffer can be split into the six displays.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
CydandClaude Opus 4.8