Bought a copy of GTA 4 yesterday and to my surprise the frame rate was like 6 fps. My config is as follows
Intel i5 760 Quad Core Processor
8 GB DDR3 1600 Mhz RAM
NVidia Geforce 8800 GTS 320 MB
It turned out that GTA was only using the dedicated memory of the card ie. 320 MB only. There was no obvious option to make the game use my surplus RAM as shared graphics memory. Finally found the solution here. Basically you need to create a new text file called commandline.txt in the GTA folder where your exe files are located. In this file add the following command without quotes “-availablevidmem 4.0”. This increased the memory available to GTA by a multiplier of 4.0 ie. now it was able to use 320×4=1280 MB of RAM. Now the game is giving me a frame rate of 40+ and am able to play the game without any problem. So yes, you me able to play GTA 4 if you graphics card does not have a lot of dedicated memory as long as you have plenty of system RAM to compensate.