12. System Interface
12.2 System Interface Description
The R4000 processor supports a 64-bit address/data interface that can construct systems ranging from a simple uniprocessor with main memory to a multiprocessor system with caches and complete cache coherency. The System interface consists of:
- 64-bit address and data bus, SysAD
- 8-bit SysAD check bus, SysADC
- 9-bit command bus, SysCmd
- eight handshake signals:
- RdRdy*, WrRdy*
- ExtRqst*, Release*
- ValidIn*, ValidOut*
- IvdAck*, IvdErr*
The processor uses the System interface to access external resources such as cache misses and uncached operations. In the case of R4000MC, the System interface also supports multiprocessor cache coherency.
Copyright 1996, MIPS Technologies, Inc. -- 21 MAR 96
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