clb wrote on 2023-08-08, 22:36:
Hmm, Chris's 3D Benchmark only 102.5 fps.. something must be capping that benchmark.
I'm super surprised the 4090 even *works* in DOS. It must have at least some legacy 16-bit vBIOS. That is encouraging, for it means a utility which "fixes" (patches) its BIOS could be made as a TSR. The same goes for other "modern" onboard BIOSes with broken VBE3, 24-bit colors, and inability to enable MTRRs on such onboard, buggy 16-bit video BIOSes. Many of these even have *all* sub 640x480 modes and *all* 8-bit modes completely disabled / non-existent! Such as all onboard AMD Ryzen vBIOSES I've ever booted into DOS.
Chris' 3D benchmark probably doesn't report higher fps because the MTRRs of the write-combining cache mode are not set or even possible to enable in that card. If MTRRs for WC could be enabled, no doubt the 4090 card would score in the thousands of fps on the Chris 3D SVGA benchmark.
I know, at least on Intel i3/i5/i7 internal onboard video, the last system that I have that can enable write-cache combining MTRRs is a Broadwell family CPU (i5-56oo) with Broadwell onboard graphics (Intel HD graphics 5600). All my 6th gen and above systems freeze when trying to enable the proper MTRRs using write-combining option of RayeR's MTRRLFBE utility, as well as other such programs.
Many of these onboard graphics also fail to set the VBE mode properly and / or lack such support. For example, on all my intel systems at 6th Gen or above, using some games to manually set 640x480 and up results in black screen and complete system freeze, while others like Quake, Quake 2, Need for Speed, etc work very well with VBE modes. I think the problem is a lack of support of either a real VESA2 linear framebuffer and / or VBE3 bugs in setting / enabling 640x480 on up -- resulting in black screen and freeze.