The Emotion Engine (EE) was developed by Toshiba Corporation and Sony licensed it; it is the main processor of the PS2. This innovative processor was designed with multimedia applications in mind, with a focus on simulation of 3D worlds. In order to let it handle a great amount of multimedia data at high speed, its bus, its cache memory, and all registers are implemented in 128 bit technology; all these components are integrated over a unique LSI chip. The EE was the first commercial processor designed with a full 128 bit structure; Dreamcast's CPU, the Hitachi SH-4, was not based on a full 128 bit structure, while at the time of the PlayStation 2 launch, normal PCs' processors usually had a 64 bit data structure.

The Emotion Engine has a frequency clock of 294.912 MHz. Its speed is not exactly 300 MHz because it must be a multiple of a required processor speed that supports DVD operations. The EE can elaborate a number of simple operations per second fairly superior to a Pentium 3 processor; the EE can handle 6.2 gigaflops (a single gigaflop equaling one billion floating point operations per second). The Emotion Engine incorporates two 64-bit integer units (IU) with a 128 bit SIMD multimedia command unit, two Vector Calculation units (VU0, VU1), an MPEG2 decoder (Image Processing Unit/IPU) and 10 high performance DMA controllers.

The power of the CPU is used to elaborate complex physical operations; the EE can generate NURBS curved surfaces and can perform 3D geometric transformations that a normal Pentium 3 would handle with a great loss of speed. Processing information on a single chip, the EE is able to transfer huge quantities of multimedia data much more quickly than a Pentium processor. The processor can handle 66 million 3D transformations per second, and can render images at 2.4 billion pixels per second. All these numbers put the PS2, at the time of its launch, next to high cost workstations used for movie editing or 3D graphics creation.