im thinking of buying a new computer specially for school and online gaming for the week-end, my choices are between a AMD Radeon HD 7420G discrete-class graphics (Feature up to 3053MB total video memory for lush images. HDMI output for flexible connectivity options) and an Intel® HD Graphics 3000. i lack of knowledge for those type of things so please help me out to make a good choice.
By your use of the word "buying" I assume you are limiting yourself to buying a computer from a retailer as supposed to building one yourself. Might I suggest looking into building one yourself as you will get more for your money and at first it might sound daunting but it is really as easy as putting lego together.
If you decide you'd like to venture into building your own pc then there are lots of benefits and given a budget, the people of Tom's will be able to come up with a good pc build to satisfy your needs.
On board graphics can be used for gaming. Intel graphics can't compete with AMD, don’t even consider gaming with intel on board graphics.
You need to understand what you are getting:
AMD discrete (onboard) graphics can do DVD/Bluray playback, media streaming and low to mid level on line gaming as well as routine computer use just fine.
The amount of memory you have on your computer has a direct impact on your frame rates. Get the best RAM you can and a lot of it.
If you think that your A4 is going to give you 100FPS at 1080i on WOW, you are fooling yourself. You can get playable framerates at low to medium settings. That’s it.