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Electrical Specifications
3.6
FSB Frequency Select Signals (BSEL[2:0])
The BSEL[2:0] signals are used to select the frequency of the processor input clock
(BCLK[1:0]). These signals should be connected to the clock chip and the appropriate
chipset on the platform. The BSEL encoding for BCLK[1:0] is shown in
Table 3.
BSEL[2:0] Encoding for BCLK Frequency
BSEL[2]
L
L
L
L
H
H
H
H
3.7
FSB Signal Groups
The FSB signals have been combined into groups by buffer type in the following
sections. AGTL+ input signals have differential input buffers, which use GTLREF as a
reference level. In this document, the term "AGTL+ Input" refers to the AGTL+ input
group as well as the AGTL+ I/O group when receiving. Similarly, "AGTL+ Output" refers
to the AGTL+ output group as well as the AGTL+ I/O group when driving.
With the implementation of a source synchronous data bus, two sets of timing
parameters need to be specified. One set is for common clock signals, which are
dependent upon the rising edge of BCLK0 (ADS#, HIT#, HITM#, etc.) and the second
set is for the source synchronous signals, which are relative to their respective strobe
lines (data and address) as well as the rising edge of BCLK0. Asychronous signals are
still present (A20M#, IGNNE#, etc.) and can become active at any time during the
clock cycle.
and asynchronous.
Datasheet
BSEL[1]
BSEL[0]
L
L
RESERVED
L
H
133 MHz
H
H
RESERVED
H
L
200 MHz
H
L
RESERVED
H
H
RESERVED
L
H
RESERVED
L
L
RESERVED
Table 4
identifies which signals are common clock, source synchronous,
BCLK Frequency
Table
3.
27
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