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>
CydandClaude Opus 4.8
e8876e521d
