Land Listing and Signal Descriptions
4.2
Alphabetical Signals Reference
Table 25.
Signal Description ( (Sheet 1 of 9))
Name
Type
Description
A[35:3]# (Address) define a 236-byte physical memory address
space. In sub-phase 1 of the address phase, these signals transmit
the address of a transaction. In sub-phase 2, these signals transmit
transaction type information. These signals must connect the
appropriate pins/lands of all agents on the processor FSB. A[35:3]#
are source synchronous signals and are latched into the receiving
buffers by ADSTB[1:0]#.
Input/
Output
A[35:3]#
On the active-to-inactive transition of RESET#, the processor
samples a subset of the A[35:3]# signals to determine power-on
configuration. See Section 6.1 for more details.
If A20M# (Address-20 Mask) is asserted, the processor masks
physical address bit 20 (A20#) before looking up a line in any
internal cache and before driving a read/write transaction on the
bus. Asserting A20M# emulates the 8086 processor's address wrap-
around at the 1-MB boundary. Assertion of A20M# is only supported
in real mode.
A20M#
Input
A20M# is an asynchronous signal. However, to ensure recognition of
this signal following an Input/Output write instruction, it must be
valid along with the TRDY# assertion of the corresponding Input/
Output Write bus transaction.
ADS# (Address Strobe) is asserted to indicate the validity of the
transaction address on the A[35:3]# and REQ[4:0]# signals. All bus
agents observe the ADS# activation to begin protocol checking,
address decode, internal snoop, or deferred reply ID match
operations associated with the new transaction.
Input/
Output
ADS#
Address strobes are used to latch A[35:3]# and REQ[4:0]# on their
rising and falling edges. Strobes are associated with signals as
shown below.
Input/
Output
Signals
Associated Strobe
ADSTB[1:0]#
REQ[4:0]#, A[16:3]#
A[35:17]#
ADSTB0#
ADSTB1#
The differential pair BCLK (Bus Clock) determines the FSB
frequency. All processor FSB agents must receive these signals to
drive their outputs and latch their inputs.
BCLK[1:0]
BNR#
Input
All external timing parameters are specified with respect to the
rising edge of BCLK0 crossing VCROSS
.
BNR# (Block Next Request) is used to assert a bus stall by any bus
agent unable to accept new bus transactions. During a bus stall, the
current bus owner cannot issue any new transactions.
Input/
Output
66
Datasheet
INTEL [ INTEL ]
