Update for the Original SimCity 4. With SimCity 4 you are the mayor (or several mayors), tasked with populating and developing tracts of lands into cities, while fulfilling the needs of fellow Sims that live in the cities. Cities are now located in regions that are divided into segments, each of which can be developed. The player has the option of starting the city in a segment of any of three area sizes, in real measurement the smallest has a length of 1 kilometers on a side, and the largest has a length of 4 kilometers on a side. The size of a region and its layout of segments can be changed in a bitmap file provided for each region.
Here is a list of what is fixed in the update:
Performance Improvements

• Zoom and rotation switching is faster in all cases, due to changes that made building graphics loading more conservative.
• AutoZoomChange:off
• Simulation and Frame rates in general are faster for many cities, due to bug fixes and performance improvements related to the traffic simulation and neighbor deals.
• The application’s memory cache is more aggressively reduced at runtime, so that memory will be freed for other uses, resulting in less paging on systems with less memory.
• Control-Shift-Alt-S (or holding down Alt while clicking on the city save button) saves the city without updating the region thumbnail and should significantly improve the game save time, especially on memory-strapped systems.
• Game default detail options have been made more conservative with respect to memory and processor speed. Because of the additions to the graphics options, your previous settings will be lost and reset with new default settings.
• The game no longer forces itself into the underground view unless you have explicitly picked an underground tool.
• Three new graphics options have been added under in-game graphics settings. They are: building detail, texture quality and building load speed. These options are initially set at conservative defaults and can be altered for your specific machine needs. Building detail will enable you to load one building style set per rank. (1 set=low, 2 sets=medium, all 3 sets=high). Texture quality will alter the textures based on the zoom level. Building load speed will enable tuning options for the rate at which buildings are loaded in memory. For example, at the low setting buildings will appear at a slower rate but there will be greater responsiveness to the mouse and scroll movements.