The M64 stands for 64bit Memory bus for memory transfers instead if the usual 128bit of the standard TNT2. It also has 110/125Mhz core/memory speed compared to the TNT2's 125/150 and TNT2 Ultra's 150/183. The card is cheat for a reason and does not overclock well (maybe 140/140 if you are lucky).
I know Unreal Turnament is having some problems with the TNT2s in Direct3D mode. They are MEMORY HOGS. The texture take up over 20 MB in system memory and are not removed correctly (supposadly the TNT2 drivers problem not the game?) so you need over 64MB memory (128 prefered) and it still runs choppy.
You should have got the Voodoo3 2000. Cheap and fast and overclocks great (mine runs stable and cool at 170 with a 486 fan) and Glide still rules!
[This message has been edited by Todd a (edited 09-30-99).]
AMD Phenom II x4 945 3Ghz | ASUS M4A77TD | 2X WD 1TB SATA 2 hard drive | 2x2GB Corsair XMS3 | nVidia GeForce 8800 GTS | ATI TV Wonder Theater Pro 550 | Antec P-160 case | Antec 650w Earth Watts | LG Blu-ray Super Drive | LG DVD RW | Windows 7 Pro