AMD-K6 datasheet(172/346 Pages) AMD

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154

Bus Cycles

Chapter 6

AMD-K6® Processor Data Sheet

20695H/0—March 1998

Preliminary Information

Locked Operation

with BOFF#

Intervention

Figure 60 on page 155 shows BOFF# asserted within a locked

read-write pair of bus cycles. In this example, the processor

asserts LOCK# with ADS# to drive a locked memory read cycle

followed by a locked memory write cycle. During the locked

memory write cycle in this example, the processor samples

BOFF# asserted. The processor immediately aborts the locked

memory write cycle and floats all its bus-driving signals,

including LOCK#. The system logic or another bus master can

initiate an inquire cycle or drive a new bus cycle one clock edge

after the clock edge on which BOFF# is sampled asserted. If the

system logic drives a BOFF#-initiated inquire cycle and hits a

modified line, the processor performs a writeback cycle before

it restarts the locked cycle (the processor asserts LOCK# during

the writeback cycle).

In Figure 60, the processor immediately restarts the aborted

locked write cycle by driving the bus off the clock edge on

which BOFF# is sampled negated. The system logic must ensure

the processor results for interrupted and uninterrupted locked

cycles are consistent. That is, the system logic must guarantee

the memory accessed by the processor is not modified during

the time another bus master controls the bus.

AMD-K6 Datasheet(PDF) 172 Page - Advanced Micro Devices