82830MP Datasheet, PDF (112/159 Pages) Intel Corporation – Intel 830MP Chipset: 82830MP Graphics and Memory Controller Hub (GMCH-M)

Intel® 830MP Chipset
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the type of Special Cycle issued by the processor. All Host initiated Special Cycles are routed to hub
interface.
Special Cycles are “posted” into the GMCH-M. The host bus transaction is terminated immediately. It
does not wait for the cycle to propagate or terminate on hub interface.
Table 27 specifies the cycle type and definition as well as the action taken by the GMCH-M when the
corresponding cycles are identified. Note that none of the host bus special cycles are propagated to the
AGP interface.
Table 27. GMCH-M Responses to Host Initiated Special Cycles
BE[7:0}#
Special Cycle Type
Action Taken
0000 0000
0000 0001
0000 0010
0000 0011
0000 0100
0000 0101
0000 0110
0000 0111
All others
NOP
Shutdown
Flush
Halt
Sync
Flush Acknowledge
Stop Clock Acknowledge
SMI Acknowledge
Reserved
This transaction has no side effects.
This transaction is issued when an agent detects a severe software
error that prevents further processing. This cycle is claimed by the
GMCH-M and propagated as a Shutdown special cycle over the hub
interface bus. This cycle is retired on the CPU bus after the associated
hub interface special cycle request packet is successfully broadcast
over hub interface.
This transaction is issued when an agent has invalidated its internal
caches without writing back any modified lines. The GMCH-M claims
this cycle and simply retires it.
This transaction is issued when an agent executes a HLT instruction
and stops program execution. This cycle is claimed by the GMCH-M
and propagated over hub interface as a Halt special cycle. This cycle is
retired on the CPU bus after the associated hub interface special cycle
request packet is successfully broadcast over hub interface.
This transaction is issued when an agent has written back all modified
lines and has invalidated its internal caches. The GMCH-M claims this
cycle and simply retires it.
This transaction is issued when an agent has completed a cache sync
and flush operation in response to an earlier FLUSH# signal assertion.
The GMCH-M claims this cycle and simply retires it.
This transaction is issued when an agent enters Stop Clock mode. This
cycle is claimed by the GMCH-M and propagated over hub interface as
a Stop Grant special cycle. This cycle is retired on the CPU bus after
the associated hub interface special cycle request packet is
successfully broadcast over hub interface.
This transaction is first issued when an agent enters the System
Management Mode (SMM). Ab[7]# is also set at this entry point. All
subsequent transactions from the CPU with Ab[7]# set are treated by
the GMCH-M as accesses to the SMM space. No corresponding cycle
is propagated to the hub interface. To exit the System Management
Mode the CPU issues another one of these cycles with the Ab[7]# bit
deasserted. The SMM space access is closed by the GMCH-M at this
point.
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Datasheet
298338-001