I have got a notebook with an i7 and a GT555M (2GB) wich the game runs great on.
and a desktop:
core: AMD A8 3870
graphics: HD6870 (1 GB)
RAM: 4 GB Kingston Hyper X
On the desktop the game should run even better. But IF I can run it (sometimes), I have to turn down the settings to avoid lag somehow.
That's not really a problem to me, but what is a problem is that it detects that my HD6870 has 2545 MB of GDDR5 while in fact it only has 1024 MB.
(I think this causes the lag issues as well, since i can run DiRT 3 on it on ultra settings 1080p)
Because of this every time I join a race, after 5 seconds or so, of low frame-rate gameplay it crashes with a GFX error saying my graphics card hasn't got enough memory.
I think the game just sees the 2545 MB and wants to use it all, and by doing that it overflows the 1024 MB which the card actually has.
Also my download manager doesn't seem to download anymore on this pc, everytime it tries to download the new SLS (which also works fine on my notebook) it says 'Failed. Requeued.' and I can't get it to download by restarting the agent/update processes or the update service.