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Intel PentiumD 950 HH80553PG0964M User Manual

Product codes
HH80553PG0964M
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Page of 112
Datasheet
31
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 
 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. 
Table 16.
GTL+ Bus Voltage Definitions
Symbol
Parameter
Min
Typ
Max
Units
Notes
1
NOTES:
1. Unless otherwise noted, all specifications in this table apply to all processor frequencies.
GTLREF_PU
GTLREF pull up resistor
124 * 0.99
124
124 * 1.01
W
2
2.
GTLREF is to be generated from V
TT
 by a voltage divider of 1% resistors (one divider for each GTLREF
land). Refer to the 
applicable platform design guide
 for additional implementation details.
GTLREF_PD
GTLREF pull down resistor
210 * 0.99
210
210 * 1.01
W
R
PULLUP
On die pull-up for 
BOOTSELECT signal
500
—
5000
W
3
3. These pull-ups are to V
TT
.
R
TT
60 Ω Platform Termination 
Resistance
51
60
66
W
4
4. R
TT
 is the on-die termination resistance measured at V
TT
/2 of the GTL+ output driver. The IMPSEL pin is used to
select a 50 Ω or 60 Ω buffer and R
TT
 value. 
50 Ω Platform Termination 
Resistance
39
50
55
W
3
COMP[7:6]
60 Ω Platform Termination
COMP Resistance
59.8
60.4
61
W
5
5. COMP resistance must be provided on the system board with 1% resistors. COMP[3:0] resistors are to V
SS
.
COMP[7:4] resistors are to V
TT
.
50 Ω Platform Termination
COMP Resistance
49.9 * 0.99
49.9
49.9 * 1.01
W
COMP[5:4]
60 Ω Platform Termination
COMP Resistance
59.8
60.4
61
W
50 Ω Platform Termination
COMP Resistance
49.9 * 0.99
49.9
49.9 * 1.01
W
COMP[3:2]
60 Ω Platform Termination
COMP Resistance
59.8
60.4
61
W
50 Ω Platform Termination
COMP Resistance
49.9 * 0.99
49.9
49.9 * 1.01
W
COMP[1:0]
60 Ω Platform Termination
COMP Resistance
59.8
60.4
61
W
50 Ω Platform Termination
COMP Resistance
49.9 * 0.99
49.9
49.9 * 1.01
W