According to Hexus, the desktop version of the GF100 GPU, which powers the GeForce GTX 480 / GTX 470, has a limited double precision speed. Indeed, the double precision speed is limited to 1/8 of single precision speed while on the HPC version of the Fermi architecture (HPC = high performance computing), the double precision speed is limited to 1/2 of single precision speed.
On Radeon HD 5000 series, the double precision speed is limited to 1/5 of single precision speed (source):
– single precision: 2720 GFlops
– double precision: 544 GFlops
For the sake of memory, GF100 / Fermi architecture implements the new IEEE 754-2008 floating-point standard, that offers full 32-bit and 64-bit precision for all instructions.