First post, by auron
Rank
Oldbie
i've read claims that the uswc bios setting essentially has the same effect as fastvid/mtrrlfbe for video performance, however in recent testing that i did and posted about here, i wasn't able to get any benefit out of it in duke3d, using a vbe 2.0 lfb mode.
FASTVID.TXT mentions this:
There is a BIOS setting that conflicts with FASTVID's write combiningfeatures. The symptom is a system lockup when mixed video and audio. If youexperience such lockups turn off "USWC write posting" (Uncached SpeculativeWrite Combining Write Posting) using the BIOS setup procedure.Many 82440 based motherboards have settings that control the same functions asFASTVID but use different terminology. "VGA Frame Buffer USWC" is the same as"Banked VGA Write Combining". "PCI Frame Buffer USWC" is the same as "LinearFramebuffer Write Combining". USWC stands for "Uncacheable Speculative WriteCombining".These BIOS's use a "failsafe" version of VGA Frame Buffer USWC that onlyenables write combining for half the banked VGA mechanism. FASTVID enableswrite combining for the entire banked VGA area resulting in betterperformance. You may find that programs that use the 16 color EGA modes don'twork properly -- but few programs use those modes anymore so you can usuallyuse FASTVID's less conservative setting.FASTVID is also more flexible than the BIOS settings. If the BIOS makes amistake about the size of the LFB you may not be able to use the LFB USWCsetting. FASTVID lets you specify the amount of memory and LFB address so youcan avoid that sort of problem.
on my bx board this is simply called "video memory cache mode", so it's not entirely clear if it would apply both on banked and linear modes, however some misdetection could have been possible as i was running both and agp and pci card for testing and switching via bios. also on a kyro ii uswc locks up the pc when loading windows.