Larrabee (microarchitecture) - Preliminary Performance Data

Preliminary Performance Data

Intel's SIGGRAPH 2008 paper describes cycle-accurate simulations (limitations of memory, caches and texture units was included) of Larrabee's projected performance. Graphs show how many 1 GHz Larrabee cores are required to maintain 60 frame/s at 1600x1200 resolution in several popular games. Roughly 25 cores are required for Gears of War with no antialiasing, 25 cores for F.E.A.R with 4x antialiasing, and 10 cores for Half-Life 2: Episode 2 with 4x antialiasing. It is likely that Larrabee will run faster than 1 GHz, so these numbers do not represent actual Larrabee cores, rather virtual timeslices of such. Another graph shows that performance on these games scales nearly linearly with the number of cores up to 32 cores. At 48 cores the performance drops to 90% of what would be expected if the linear relationship continued.

A June 2007 PC Watch article suggested that the first Larrabee chips would feature 32 x86 processor cores and come out in late 2009, fabricated on a 45 nanometer process. Chips with a few defective cores due to yield issues would be sold as a 24-core version. Later in 2010, Larrabee would be shrunk for a 32 nanometer fabrication process to enable a 48 core version.

The last statement of performance can be calculated (theoretically this is maximum possible performance) as follows: 32 cores × 16 single-precision float SIMD/core × 2 FLOP (fused multiply-add) × 2 GHz = 2 TFLOPS