Speed and Performance of LINQ

I was wondering today if anyone had produced any benchmarks on the speed and performance of LINQ, so I had a look around and found that LINQ 2 SQL is 4 times faster than the Entity Framework.  Why is this?  It is due the the fact that the Entity Framework is a more generic solution, where as LINQ to SQL can be more fine tuned to the underlying database structure.

Here are a few links I found that might explain things in more details

ADO.NET Entity Framework Performance Comparison

How Slow is ‘Slow’?