Electrical Specifications
30
Datasheet
.
2.7.3.2
GTL+ Front Side Bus Specifications
In most cases, termination resistors are not required as these are integrated into the
processor silicon. See
for details on which GTL+ signals do not include on-die
termination.
Valid high and low levels are determined by the input buffers by comparing with a
reference voltage called GTLREF.
lists the GTLREF specifications. The GTL+
reference voltage (GTLREF) should be generated on the system board using high
precision voltage divider circuits.
NOTES:
1.
Unless otherwise noted, all specifications in this table apply to all processor frequencies.
2.
GTLREF is to be generated from VTT by a voltage divider of 1% resistors. If an Variable
GTLREF circuit is used on the board the GTLREF lands connected to the Variable GTLREF
circuit may require different resistor values. Each GTLREF land must be connected.
3.
R
TT
is the on-die termination resistance measured at V
TT
/3 of the GTL+ output driver.
4.
COMP resistance must be provided on the system board with 1% resistors. COMP[3:0] and
COMP8 resistors are to V
SS
.
Table 2-12. PECI DC Electrical Limits
Symbol
Definition and Conditions
Min
Max
Units
Notes
1
NOTES:
1. V
TT
supplies the PECI interface. PECI behavior does not affect V
TT
min/max specifications. Refer
to
TT
specifications.
V
in
Input Voltage Range
-0.15
V
TT
V
V
hysteresis
Hysteresis
0.1 * V
TT
—
V
2
2. The leakage specification applies to powered devices on the PECI bus.
V
n
Negative-edge threshold voltage
0.275 * V
TT
0.500 * V
TT
V
V
p
Positive-edge threshold voltage
0.550 * V
TT
0.725 * V
TT
V
I
source
High level output source
(V
OH
= 0.75 * V
TT
)
-6.0
N/A
mA
I
sink
Low level output sink
(V
OL
= 0.25 * V
TT
)
0.5
1.0
mA
I
leak+
High impedance state leakage to V
TT
N/A
50
µA
3
3. The input buffers use a Schmitt-triggered input design for improved noise immunity.
4. One node is counted for each client and one node for the system host. Extended trace lengths
might appear as additional nodes.
I
leak-
High impedance leakage to GND
N/A
10
µA
2
C
bus
Bus capacitance per node
—
10
pF
4
V
noise
Signal noise immunity above 300 MHz
0.1 * V
TT
—
V
p-p
Table 2-13. GTL+ Bus Resistance Definitions
Symbol
Parameter
Min
Typ
Max
Units Notes
1
GTLREF_PU GTLREF pull up resistor
57.6 * 0.99
57.6
57.6 * 1.01
Ω
2
GTLREF_PD GTLREF pull down resistor
100 * 0.99
100
100 * 1.01
Ω
2
R
TT
Termination Resistance
45
50
55
Ω
3
COMP[3:0]
COMP Resistance
49.40
49.90
50.40
Ω
4
COMP8
COMP Resistance
24.65
24.90
25.15
Ω
4
Содержание Core2 Extreme QX9000 Series
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