The Socket 603 utilized the pin grid array and was used by Intel for the Xeon processors. Intel also manufactured a Socket 604 processor that was compatible with Socket 603 processors, but the Socket 604 processor could not be used with a Socket 603 motherboard. Intel distinguishes between the two by stating Socket 603 is a low cost, low risk, and high volume manufactured processor.
All Socket 603 processors were designed for use in workstation computers and servers. They were designed to be more robust and run for extended periods of time in high use environments. Socket 603 only supported a front-side bus speed of 400 MHz and ranged in speed from 1.4 GHz to 3.0 GHz.