Beginning with SQL Server 2008 R2, there’s a significant difference in the amount of memory that SQL Server can allocate from the OS to its buffer cache (Buffer Pool). An Standard Edition will not grow it further than 64GB, no matter how much physical memory is available to the system on which the instance of SQL runs. That is a limit imposed in the code (hardcoded). The Enterprise Edition though, can allocate up to 2TB for the buffer pool (provided the maximum limits set by the OS are not lower than those 2TB.)
Therefore, if you want your instance of SQL Server to cache in memory over 64GB worth of data, not only you will need an edition of Windows that supports that amount of physical memory, but also will require SQL to run an Enterprise Edition (or a Developer Edition or an Evaluation Edition, both of which behave exactly like the Enterprise does. The only difference among them three is their licensing.)
This post is part of the a series I decided to call “Understanding the value of the Enterprise Edition, one feature at a time” which I started in September 2011 and will grow on a weekly basis, having a new post incorporated to the family every Friday.