Internal Buses The PowerPC 440EP

Internal Buses
The PowerPC 440EP features five standard on-chip buses: two Processor Local Buses (PLBs), two On-Chip Peripheral Buses (OPBs), and the Device Control Register Bus (DCR). The high performance, high bandwidth cores such as the PowerPC 440 processor core, the DDR SDRAM memory controller, and the PCI bridge connect to the PLBs. The primary OPB hosts lower data rate peripherals. The secondary OPB is dedicated to USB 2.0 and DMA. The daisy-chained DCR provides a lower bandwidth path for passing status and control information between

the processor core and the other on-chip cores.
Features include:
• PLB4
– 128-bit implementation of the PLB architecture
– Separate and simultaneous read and write data paths
– 36-bit address
– Simultaneous control, address, and data phases
– Four levels of pipelining
– Byte-enable capability supporting unaligned transfers
– 32- and 64-byte burst transfers
– 133MHz, maximum 4.25GB/s (simultaneous read and write)
– Processor:bus clock ratios of N:1 and N:2
• PLB3
– 64-bit implementation of the PLB architecture
– 32-bit address
– 133MHz (1:1 ratio with PLB 128), maximum 1.1GB/s (no simultaneous read and write)
• OPB (2)
– 32-bit data path
– 32-bit address
– 66.66MHz
• DCR
– 32-bit data path
– 10-bit address