Overview
The MPC7457 is the fourth implementation of the fourth generation (G4) microprocessors from Freescale. The MPC7457 implements the full PowerPC 32-bit architecture and is targeted at networking and computing systems applications. The MPC7457 consists of a processor core, a 512-Kbyte L2, and an internal L3 tag and controller that support a glueless backside L3 cache through a dedicated high-bandwidth interface. The MPC7447 is identical to the MPC7457 except that it does not support the L3 cache interface.
Figure 1 shows a block diagram of the MPC7457. The core is a high-performance superscalar design supporting a double-precision floating-point unit and a SIMD multimedia unit.

The memory storage subsystem supports the MPX bus protocol and a subset of the 60x bus protocol to main memory and other system resources. The L3 interface supports 1, 2, or 4 Mbytes of external SRAM for L3 cache and/or private memory data. For systems implementing 4 Mbytes of SRAM, a maximum of 2 Mbytes may be used as cache; the remaining 2 Mbytes must be private memory.
Note that the MPC7457 is a footprint-compatible, drop-in replacement in a MPC7455 application if the core power supply is 1.3 V.