yes u can u can OC but u must have big size Memory for memory sharing (max 512 MB & keep NB temperature !
In bios select
- UMA+Sideport set in 512MB ,
- other side control Clock set 700~990 not over, i have Mobo onboard under OC 42% max get 990 succes on 3Dmark06
- HT link 2500 above & max 2800 better get more score in 3Dmark06 (i have HD 4290 )
- Test your VGA with 3Dmark06 & how much u get Score ! hmm... maybe max u can get 2844
Did you try hybrid crossfireX on your PC? If you have IGP HD 4290 you must have 890G chipset or something like that and that suports hybrid crossfireX.