The Raspberry Pi SoC (System on Chip) is a Broadcom BCM2835.
This contains an ARM1176JZFS (ARM11), with floating point, running at 700Mhz (over clocking to 800MHz is often OK if needed).
Software needs to be compiled for ARMv6 to be used with the Raspberry Pi.
Videocore 4 GPU.
Capable of BluRay quality playback, using H.264 at 40MBits/s.
Fast 3D core accessed using the supplied OpenGL ES2.0 and OpenVG libraries.
Open GL ES 2.0, hardware-accelerated OpenVG, and 1080p30 H.264 high-profile decode.