It's 1gb and I overclocked gpu to 700mhz and 900mhz(memory). Can't I even get 15-20 fps?
to give you an idea, this gpu is about 100gflops according to gpuboss
the ps3 which is a 10 year old gaming console has a gpu with 300gflops and gta5 is optimized for that and it gets less than 30fps on low graphics 720p