True Performance Index (TPI) is used to measure the performance of central processing unit

Central processing unit

The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

 chips produced by manufacturer AMD. For example, the Athlon

Athlon

Athlon is the brand name applied to a series of x86-compatible microprocessors designed and manufactured by Advanced Micro Devices . The original Athlon was the first seventh-generation x86 processor and, in a first, retained the initial performance lead it had over Intel's competing processors...

 3400+ chip has a TPI rating of 3400, hence the name of the model. The True Performance Index is designed to help consumers choose AMD CPU products by comparing them to processors' speeds from competing manufacturers (Intel).