|The K6 is very old. It's wasn't rated in GHz, it was in MHz, unless you mean 0.5 GHz?|
There were several K6 versions - the original K6, K6-2, K6-2+ & K6-3, K6-3+. They ran at different speeds - 166 thru 550MHz. They either used 72-pin SIMM memory or 168-pin SDR-SDRAM (PC66, PC100 or PC133), depending on the motherboard.