The diffrence is ready for this , (lord K knows how obsessed i am )
GT
350mhz core
1000mhz memory
2.0ms Ram , 1 Slot cooler , one molex
Ultra
400-450 mhz core
1100-1200 mhz memory
1.6ms RAM , Bigger cooler , 2 molex
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Buy the XFX ultra its memory is also clocked at 1200mhz . and can be overclocked to something like . 475 / 1300 , Which is insane . If you are playing at 1600 - 1200 you will notice diffrence from the ultra - gt . but anything under the ultra - gt are 2fps apart.