Mario Kart 64 - 0.95 F3DEX - Wrong gsSPCullDisplayList binary

[DeadHamster35]

Mario Kart 64's USA release uses an early version of F3DEX labelled 0.95. This is not identical to the more common 1.21 F3DEX on a binary level - one of the quirks of this version is the inclusion of the full gsSPQuadrangle command, which starting with 1.21 F3DEX is converted at compilation to a gsSPTriangle2. This is emulated correctly which is apparently handled via a special microcode -

GLideN64/src/GBI.cpp

Line 57 in cb6e6cb

{ F3DEX, false, false, true, 0x0ace4c3f }, // Mario Kart 64

Recently (today) it was discovered that another command has a difference in the binary layout; gsSPCullDisplayList appears to use the same binary from F3D and not the later 1.21 F3DEX versions.

To test a region of 8 vertices, the correct 0.95 F3DEX binary command and parameters should read -
BE 00 00 00 00 00 01 40

#define gsSPCullDisplayList(vstart,vend)				
{									
	_SHIFTL(G_CULLDL, 24, 8) | ((0x0f & (vstart))*40), 		
	((0x0f & ((vend)+1))*40)					
}

whereas GLideN64 currently (incorrectly) expects the 1.21 binary format -
BE 00 00 00 00 00 00 0E

#define gsSPCullDisplayList(vstart,vend)				
{									
	_SHIFTL(G_CULLDL, 24, 8) | _SHIFTL((vstart)*2, 0, 16),		
	_SHIFTL((vend)*2, 0, 16)					
}

Using the newer 1.21 F3DEX binary leads to a crash on original hardware as it checks for an invalid number of verts. This has gone unnoticed as the original game never uses the gsSPCullDisplayList command, however this leads to a discrepancy when attempting to design mods that are compatible with both modern emulators and console.

[gonetz]

Thanks for the info!
I added separate init for 0.95 F3DEX: #2862