AMD-K6 Datasheet, PDF (121/346 Pages) Advanced Micro Devices – AMD-K6 Processor

20695H/0—March 1998
Preliminary Information
AMD-K6^® Processor Data Sheet
5.31
Summary
Sampled
KEN# (Cache Enable)
Input
If KEN # is sampled asserted, it indicates that the address
presented by the processor is cacheable. If KEN # is sampled
asserted and the processor intends to perform a cache-line fill
(signified by the assertion of CACHE#), the processor executes
a 32-byte burst read cycle and expects to sample BRDY #
asserted a total of four times. If KEN # is sampled negated
during a read cycle, a single-transfer cycle is executed and the
processor does not cache the data. For write cycles, CACHE# is
asserted to indicate the current bus cycle is a modified
cache-line writeback. KEN# is ignored during writebacks.
If PCD is asserted during a bus cycle, the processor does not
cache any data read during that cycle, regardless of the state of
KEN#. (See “PCD (Page Cache Disable)” on page 107 for more
details.)
If the processor has sampled the state of KEN# during a cycle,
and that cycle is aborted due to the sampling of BOFF #
asserted, the system logic must ensure that KEN# is sampled in
the same state when the processor restarts the aborted cycle.
KEN # is sampled on the clock edge on which the first BRDY # or
NA # of a read cycle is sampled asserted. If the read cycle is a
burst, KEN # is ignored during the last three assertions of
BRDY #. KEN # is sampled during read cycles only when
CACHE # is asserted.
Chapter 5
Signal Descriptions
103