Cpu+onboard Gpu

Hi,this is a question regarding both GPU and CPU so put it here. I am looking at getting either a i7 or i5,i noticed that they come with onboard HD grapics. My question is,do these onboard graphics run along side your normal GPU or would you disable them in the bios. Sorry if its a dumb question,its been a long time since ive had a intel GPU.
Many thanks.

Do you mean you going to buy a system that has either an I7 or an I5 and the system has only on board graphics?

No,the system i am building will have a stand alone GPU but while having a look at some CPU`S i have found a i5 that no longer has the onboard graphics so i think i will end up getting that one.
I do have another question tho,the Memory Controller on the CPU is Dual channel DDR3 800/1066/1333/1600 MHz,so does this mean(and this is going to sound like a right noob question) that say if i was to buy ram at Dual Channel 1866MHz it would only go as high as 1600MHz.

you can use the onboard graphics as well as a discrete gpu if the motherboard supports it

using software called virtu--this is meant to speed up video conversion

no the 1866mhz ram wouldnt only go as high as 1600mhz

officially up to 1600mhz is supported but speeds over 2000mhz can run depending on the motherboard but its

classed as overclocking the ram

but ram over 1600mhz is much more expensive and you wont really notice the difference anyway in real life

use--though you would see a higher benchmark score