I'm currently using Ubuntu 12.04 64bit. After installing ATI/AMD proprietary FGLRX graphics drivers via Additional Drivers, I checked the status of my VGA card using lspci -v. Here's the output:

02:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI M96 [Mobility Radeon HD 4650] (prog-if 00 [VGA controller])

Subsystem: Dell Device 0456     
Flags: bus master, fast devsel, latency    0, IRQ 46    
Memory at d0000000 (32-bit, prefetchable)    [size=256M]    
I/O ports at 2000 [size=256]    
Memory at cfef0000    (32-bit, non-prefetchable) [size=64K]     
[virtual] Expansion ROM at cfe00000 [disabled] [size=128K]  
Capabilities: 
Kernel driver in use: fglrx_pci     
Kernel modules: fglrx, radeon

As mentioned in the title, my VGA card is 1GB and yet my computer only recognizes 256MB. My question is: "How to make my computer fully recognize the capacity of my ATI Mobility Radeon HD 4650 (1GB)?"