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MIPS R10000 Microprocessor User's Manual - SGI TechPubs Library

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132 Chapter 6.<br />

External Request Protocol<br />

Errata<br />

An external agent issues an external request when it requires a resource within the<br />

processor. The external agent refers to any device attached to the processor system<br />

interface. It may be memory interface or cluster coordinator ASIC, or another<br />

processor residing on the cluster bus.<br />

An external agent may only issue an external request to the processor when the<br />

System interface is in slave state. If the System interface is not already in slave<br />

state, the external agent must first negate SysGnt* and then wait for the processor<br />

to assert SysRel*. If the System interface is already in slave state, the external<br />

agent may issue an external request immediately. The total number of outstanding<br />

external requests, including interventions, allocate request numbers, and<br />

invalidates, cannot exceed eight.<br />

External requests may be accepted by the processor in adjacent SysClk cycles.<br />

External intervention and invalidate requests are considered external coherency<br />

requests.<br />

Version 2.0 of January 29, 1997 <strong>MIPS</strong> <strong>R10000</strong> <strong>Microprocessor</strong> <strong>User's</strong> <strong>Manual</strong>

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