Try that, it probably fixes your problem. It was working for me on my Voodoo3 and Voodoo5.
Open the Registry Editor
Navigate to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Display\0000\TIMINGS

look for the 1920x1080 60 Hz timing where is says "2368,1952,2096,1125,1083,1086,12,159840000,6000,8,31714"
change it to "2048,1960,1992,1232,1141,1144,4,151390000,6000,8,30668"

alternatively typing in "GTF" instead of the number should also work as well

restart Windows

now it may work 😀

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For other widescreen resolutions:

Add resolutions in HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Display\0000\MODES

just look how the others look like

and timings in HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Display\0000\TIMINGS

16:10 resolution timings for 60 Hz:
1280x800 60Hz: 1680,1344,1480,828,801,804,4,83460000,6000,8,21295
1440x900 60Hz: 1904,1520,1672,932,901,904,4,106470000,6000,8,24492
1600x1024 60Hz: 2088,1632,1792,1070,1027,1030,12,134049600,6000,8,28063
1680x1050 60Hz: 2256,1784,1968,1087,1051,1054,4,147140000,6000,8,29926
1920x1200 60Hz: 2592,2048,2256,1242,1201,1204,4,193160000,6000,8,35871

"GTF" should also work instead of the timing number

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If you want to calculate the timing for some other resolutions check this out.

http://tinyvga.com/vga-timing

Select resolution and calculate timings:

1: Horizontal Whole line (in pixels)
2: H Visible area + H Front porch (in pixels)
3: H Visible area + H Front porch + H Sync pulse (in pixels)
4: Vertical Whole frame (in lines)
5: V Visible area + V Front porch (in lines)
6: V Visible area + V Front porch + V Sync pulse (in lines)
7: Flags (+1: scan line double, +2 interlace, +4 negative hsync, +8 negative vsync)
8: Pixel freq. (*1000000)
9: Screen refresh rate (*100) (field not actually used?)
10: Char Width (Always 8?)
11: Checksum (all proceeding numbers added together, but ignoring last 4 zeros of pixel frequency).

If the checksum is wrong, the driver will ignore the specified timing
and use the closest default timing built in to the driver.

But "GTF" instead of the timing number should work in most cases I guess.