Pentium 4 with L3 cache
A document can be found on the INTEL website which provides information on the Pentium 4's cache architecture. After that it is possible to equip the Pentium with an L2 cache of up to 1 MByte.
In addition, there will probably also be another cache, the L3 cache could even support up to 4 MByte.
Presumably, INTEL will change the base again next year. The Pentium 4 will have a socket with 423 pins, but its successor (code name Prescott) will need a slot with 479 pins.