Found this when googleing: http://www.amd-drivers.com/download-RadeonHD7640G-mobility-driver-for-Windows8-64bit.html
I can't guarantee though that this is the right one.
Is this an older computer or did you just get it ? It could be that the drivers for Windows 8 don't work well for older models.
Are you using custom content or mods in your game ?
Are you willing to try a third party tool ? There's a tool called crash log analyzer (just google).
It's not a magic tool that can stop the crashes but it can give an indication to where the error lies. Just copy the errors you get to the clipboard and post them here.
This tool is not supported by EA so you'll be using it at your own risk