Illustrator CS6 – Adobe Mercury Performance System
The Adobe Mercury Performance system is a combination of solutions that makes Illustrator faster, more responsive, and able to handle larger files.
64-bit native support
Makes general processing faster on 64-bit Macintosh and Windows operating systems. Illustrator can now take advantage of RAM beyond 3 GB.
Handle larger files
Concurrent handling of large files is less likely to cause errors, like out-of-memory exceptions. Complex tasks, such as creating package designs, large-format graphics, or cartography, are better handled.
Improved memory handling
Reduces out-of-memory errors for operations such as rasterization, export, and working on several large files simultaneously.
https://adobecs6blog.wordpress.com/2012/06/22/whats-new-in-illustrator/