Two GTX570's in SLI - I'm surprised all the newfangled overlays and postprocessed effects ran so well, though the real surprise is that the CPU-side simulation didn't eat my computer for lunch. SimCity 4 for mid-sized cities and above still kills a i7.
Sim City 4 is single threaded and only uses one core, which is why it is so slow on new hardware.
The other major drawback to Sim City 4 is that there is a bug which prevents rich ($$$) Sims from working in the High Tech industry. The only way to fix this is to use a 3rd party mod.
There are many problems with SC4. The most egregious one (for me anyways, someone who likes to build insanely dense cities) is that pathfinding "bug".
The short version is, your sims must find a reasonable commute from home to work, otherwise your economy stagnants and unemployment runs rampant. SC4's pathfinding heuristic disallows a sim from going backwards to go forwards.
This creates many transportation deadzones and a lot of unintuitive bottlenecks. You will literally see sims live directly next to a subway station that takes them directly to work, but they will drive instead.
There is a mod to fix this, but the performance impact is expectedly awful.
Ugh. It's been a while since I played, so I had forgotten about this.
It's not as bad as you described it. It's even worse.
The hack the creators of SC4 used to get around the problem of traveling the same path twice in one trip is responsible for a large waste of CPU cycles. Essentially, the hack allows the Sim to "forget" how he got to a certain location and start a new trip to the final destination. The downside is that this is that all of the information from the previous leg of the trip is lost, and the algorithm must run again. There isn't a 1:1 ratio between the amount of citizens and CPU cycles wasted, because as your city grows the path each citizen must take becomes more complex and consumes more cycles.
You can read more about it here, at a third party fan site. [1]
