Intel Corporation

Nagraj Palasamudram

James Nadir

Yong Ju Lee

A cache controller sits in parallel with a microprocessor bus and includes a tag RAM for associatively searching a directory for cache data-array addresses. Two normal address latches are provided to capture a cycle address in case the current cycle is extended by a pending tag RAM access. At any time, except when the next cycle has started, but during which the current cycle is in progress, one latch is open to an input buffer such that the input address is latched by that latch. The other latch holds the current cycle address until the cycle ends. The current cycle can be extended with snoops. The current cycle address has to be maintained as long as the cycle is still in progress. In the meantime, the external cycle might have ended and a next cycle started. The second address latch is used to capture the address corresponding to this new cycle. As signal selects which of the two latches will supply the address via a MUX to the tag RAM. Logic switches the two input address latches so that the tag RAM sees a constant address for the duration of a cycle while at the same time a new cycle address can be received.

Growing community of inventors

San Jose, CA, United States of America

Nagraj Palasamudram