The Unabridged Pentium 4 IA32 Processor Genealogy

486 Flavors

The 486 processor was produced in the following flavors (shown in order of introduction; note that all of them incorporated an internal cache):

• 486SX/487SX. The original incarnation of the 486 did not have an integrated FPU. Rather, the system board included a socket into which the 487 numeric coprocessor could be installed. In fact, the 487 was a full-blown 486 processor with an integrated x87 FPU. When installed, it asserted a signal to the 486 that caused it to float all of its output drivers so the 487 could take over the role of the system processor. This processor integrated an internal, unified, write-through code/data cache.

• 486SX2. This version of the 486SX was the first IA32 processor to use an internal clock multiplier. ...