Does this happen with both Glide and D3D?

If I recall, I tested it with D3D using the Matrox G200 and glide using the Voodoo1 and Voodoo2. Same result - hangs. I could try disabling all the Cyrix features to see if it is one in particular, though it could also be none of them. Better if there is a software patch though.

Weird. I'm pretty sure there never was a 5x86 patch, but 6x86 patches were fairly common for games at the time, usually because said games thought they were running on a 486.
Perhaps if you locate such a patch for Turok it could fix the issues.

I thought the problem was the Cyrix chips aren't instruction set compatible with Pentium and so some software blows up because of programmers not thinking beyond Intel.

The Cyrix 5x86 literature says that it is x86 and x87 compatible, whatever that means exactly. Turok works with the Am5x86 and the Intel DX4, so it seems to me that the issue is not specific to Pentium instructions. I have also run into cases whereby graphic card drivers have worked with the Am5x86 but not the Cx5x86. It would be nice if there was some workaround for this.

I have tracked the issue with Turok down to the FP_FAST feature of the Cyrix 5x86. Disable this feature and the game won't crash. I also noticed this issue with Quake 2. These two games don't like FP_FAST for whatever reason. I never had any other issues with FP_FAST in any other game. Interestingly, if using a SiS 496/497 based motherboard, FP_FAST worked fine with Quake 2 and a cx5x86-133. Perhaps the combination of UMC 8881 + Cyrix 5x86 + (Turok or Quake 2) doesn't like FP_FAST. Turok 2 is fine.