AMD K5 PR133
This is the second generation AMD K5 that is based on the 5k86 core. It has been optimized a bit and should be faster per MHz than the original one. Because of this AMD used the PR number (Performance Rating) to indicate performance. The original AMD K5 PR75, PR90 and PR100 ran at respectively 75MHz, 90MHz and 100MHz. This K5 PR133 works at 100MHz and the PR166 at 116MHz.
Don't confuse the 5k86 core with the name of the AMD 5k86 P75 which is just an older AMD SSA/5 core but with a different name attached to the CPU.

