What is Vram and its use


Jul 17, 2013
ok..so this is the config of my laptop
AMD trinity A8 4500
quad core processor 1.9ghz(can be overclocked with turbocore upto 2.8ghz)
RAM 4GB ddr3 1600mhz
Graphics card:7640G(512mb integrated)+7670m(2GB dedicated)
15.6“ led 1366*768resolution

So when i play heavy games like crysis 3,farcry 3,assasins creed,nfs most wanted 2012 with both graphics enabled it lags..Farcry 3 gives the playable frame rate at medium settings,assassins creed lags a little in medium settings,nfs mostwanted lags a lot,and crysis 3 can be playable at medium settings...
BUT when i disable dual graphics and select the default apu 7640g the games that lags runs at breeze,farcry 3 runs so smooth at high settings,assassins creed and nfs mostwanted runs so smooth at highest settings and so do crysis 3 at high settings in desktop resolution..
I mean to say HOW CAN IT BE POSSIBLE???
the total memory in the graphics section shows that it has 4GB memory.i think the other 1.5 GB is the vram but 7640G is the integrated one and only 512mb .So please make me understand why runnings the games at crossfire lags.
And their is only two options for selection the gpu..either the integrated apu or both.is their any solution for selecting the dedicated one..i have the latest drivers installed..pls answer.