Both models
i5-2520M and
E3-1225 are based on
Sandy Bridge architecture.
"Sandy Bridge codename was originally ""Gesher"". The development began in 2005 and four years later, the first Sandy Bridge CPU was presented. The most prominent features are Intel Turbo Boost 2.0, AES encryption and SHA-1 hashing acceleration, Advanced Vector Extensions (AVX) 256-bit instruction set and the ability to have up to 8 physical cores or 16 logical cores through Hyper-Threading."
Using the multithread performance as a reference, the i5-2520M gets a score of
34.2 k points while the E3-1225 gets
44.8 k points.
Summarizing, the
E3-1225 is
1.3 times faster than the
i5-2520M . To get a proper comparison between both models, take a look to the data shown below.