Game uses voxel engine and does not rely on hardware-acceleration via a 3D graphics card thus all the burden of rendering the game is up to your processor. Thanks to this computers back in the day were just barely able to run it despite game's low resolution.

Game runs very well with HIGH RES v3 patch if you have this points in mind--->

*copy all files from patch to game directory
*you have to edit and save the Pentium III 500 64 Mb.ini and the Pentium III 550+ 64 Mb.ini
in game folder to the follow:

__________________________________________________________________________________________

[performance]
resolution=1024x768
cinemascope=false

crowdlevel=true
ambientsounds=true
bumpmapping=true
highanimationdetail=true

antialiasing=high
chardetail=high
objectdetail=high
prq=high
dof=high

doc=high

__________________________________________________________________________________________

*first start the patch and choose 1024x768 resolution, chang options, then launch game
*at launch menu go to graphic settings and select "Pentium III 550+ 64 Mb"
*now, keep in mind, that this menu has an heavy bug.
YOU HAVE TO LEAVE ALL OPTIONS ON "LOW" to play the game in High Res
with high distance!!!

I use notebook to play, my GT 555 has a flickering too, but i yoiu use the option to run on the intel HD, it just run fine.