Once you have installed the v1.1.640 patch, your game is fully updated. However, you are not done optimizing. The original SimCity 4.exe is a 32-bit application, which means it can only use approximately 2GB of RAM. This often causes the game to crash to desktop (CTD) when your cities become large or when you have installed many plugins.
EA no longer hosts the patch directly, but these are safe, widely-used sources in the SimCity 4 community:
In the box, add a space after the last quotation mark and paste: -CPUCount:1 2. Set Modern Resolutions
If you own the digital version of SimCity 4, the version is already 1.1.640, so you do not need to download this patch. Patch 1.1.640 - SC4 Devotion
