There are two types of caches, L1 and L2. In the 80486 a small internal cache cache was implemented on the processor itself. This was called the L1 cache and was only 8k. There was also an external cache called a L2 cache. Starting with the Pentium Pro, and also on the Pentium II, a 512k onboard L2 cache was also included.
Every processor has a set of commands that it knows.
As each family of processors increases, more commands are added to the instruction set. All the previous commands are left intact to provide for backward compatiblility with programs written for older processors. The newest instruction set is called MMX, and released by Intel. MMX stands for Multimedia Extensions. In order for new instruction sets to be effective, new software has to be written to take advantage of the new commands.