Good morning, My mate is upgrading his 5850 to a gtx 660 to play skyrim and the witcher running lots of mods at 1080p, his cpu is a 1155 pentium g840- will the cpu hold back the gpu? Cheers.
Depends on resolution and the type of mods he has installed. In the normal version of both he will see increased FPS.
I've been trying to get him to buy a used i5 cpu but they are still a bit expensive for him, will an i3 be much of an improvement from the pentium?
Pentium and i3 are really very very close and probably not worthwhile upgrade. Hyperthreading generally dosen't help in gaming and a better igpu won't matter either and those are the only major differences between them. Unless the games they like are heavy multithreaded on the CPU the Pentium shouldn't be that bad and won't be a bottleneck otherwise.
See if you can go second hand bud, I picked up an i5 3330 on the bay for just under £90! Or even some of the old SB stuff floating about is going sub £80. That brings it into contention with a new i3.
I tested a 1155 Celeron with a GTX 480 (which IIRC is around the same as a GTX 660). I used a 1155 Celeron and a I7 950... Any way, depends on the game really. Skyrim actually did pretty well though IIRC. But he will most certainly see a bottle neck of sorts, even in non CPU dependent games.