300 Datasheet, PDF (28/95 Pages) DB Lectro Inc – SCREW TYPE SERIES

Electrical Specifications
2.6.3.1
GTL+ Front Side Bus Specifications
In most cases, termination resistors are not required as these are integrated into the
processor silicon. See Table 8 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. Table 16 lists the GTLREF specifications. The GTL+
Reference voltage (GTLREF) should be generated on the system board using high
precision voltage divider circuits.
Table 16. GTL+ Bus Voltage Definitions
Symbol
Parameter
Min
Typ
Max
Units Notes¹
GTLREF_PU GTLREF pull up resistor
GTLREF_PD GTLREF pull down resistor
124 * 0.99 124 124 * 1.01 Ω
2,3
210 * 0.99 210 210 * 1.01 Ω
2,3
R_PULLUP
On die pull-up for BOOTSELECT
signal
500
—
5000
Ω
4
R_TT
COMP[1:0]
60 Ω Platform Termination
Resistance
50 Ω Platform Termination
Resistance
60 Ω Platform Termination
COMP Resistance
50 Ω Platform Termination
COMP Resistance
51
60
66
Ω
5
39
50
55
Ω
5
59.8
60.4
61
Ω
6
49.9 * 0.99 49.9 49.9 * 1.01 Ω
6
COMP[5:4]
60 Ω Platform Termination
COMP Resistance
50 Ω Platform Termination
COMP Resistance
59.8
60.4
61
Ω
6
49.9 * 0.99 49.9 49.9 * 1.01 Ω
6
NOTES:
1. Unless otherwise noted, all specifications in this table apply to all processor frequencies.
2. GTLREF is to be generated from V_TT by a voltage divider of 1% resistors (one divider for each GTLREF
land).
3. For Intel 865 Express chipset LGA775 boards only, the GTLREF_PU should be 49.9 Ω 1%, and the GTLREF_PD should
be 100 Ω 1%.
4. These pull-ups are to V_TT.
5. R_TT is the on-die termination resistance measured at V_TT/2 of the GTL+ output driver. The IMPSEL land
is used to select a 50 Ω or 60 Ω buffer and R_TT value.
6. COMP resistance must be provided on the system board with 1% resistors. COMP[1:0] resistors are
to V_SS. COMP[5:4] resistors are to V_TT.
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Datasheet