The specs on the 750 and 750Ti are now official, and somewhat hard to believe.
GTX 750Ti:
640 cores
60W TDP
1020MHz base/1085MHz Boost
GTX 750:
512 cores
55W TDP
1020MHz base/1085MHz Boost
These both use the same 28nm GM107 chip.
Performance? Heh. During Nvidia's conference, they showed a slide comparing frames per second while playing Call of Duty: Ghosts.
The HD 4600 IGP scored 10 FPS
A GT 640 (65W version) scored 22 FPS
And the 750Ti scored 51 FPS
This worries me. The performance increase is simply too good in games. When Nvidia went from the 500 to the 600 series, gaming performance increased alot there too, but the 600 series was worse at crunching. Supposedly these new Maxwell chips in the 750 and 750Ti offer 35% more performance per core while using half the power. That's just too much. Something's wrong somewhere.