The CPU was a 6510 from MOS Technology (who were a wholly owned subsiduary of Commodore at this time(?)). The C64 had 64 kilobytes of RAM as standard and a 40-column text, 320x200 pixel display generating composite video, usually connected to a television.
DMA-based memory expanders for the C64 (and C128) allowed 128, 256, and 512 kb of RAM. Several third party manufacturers produce accelerators and RAM expanders for the C64 and C128. (Some, risking a holy war, compare this to putting a brick on roller-skates). Such accelerators come in speeds up to 20MHz (20 times the original) and RAM expanders to 16MB.
See also Commodore 65.
["Assembly language programming with the Commodore 64", Marvin L. De Jong].