Intel 4 515/515J JM80547PE0771M User Manual

34

Termination resistors are not required for most GTL+ signals, as these are integrated into the 
processor silicon.Valid high and low levels are determined by the input buffers which compare a 
signal’s voltage 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.

§

1.

Unless otherwise noted, all specifications in this table apply to all processor frequencies.

GTLREF

Bus Reference 
Voltage

(0.98 * 0.67) * V

TT

0.67 * V

TT

(1.02 * 0.67) * V

TT

V

2, 3, 4,

 

5

2.

The tolerances for this specification have been stated generically to enable the system designer to calculate the minimum
and maximum values across the range of V

TT

.

3.

GTLREF should be generated from V

TT

 by a voltage divider of 1% resistors or 1% matched resistors.

4.

The V

TT

 referred to in these specifications is the instantaneous V

TT

.

5.

The Intel

®

 915G/915GV/915P and 910GL Express chipset platforms use a pull-up resistor of 100

Ω and a pull-down resistor

of 210

Ω. Contact your Intel representative for further details and documentation. 

R

PULLUP

On die pullup for 
BOOTSELECT 
signal

500

—

5000

Ω

6

6.

These pull-ups are to V

TT

.

R

TT

Termination 
Resistance

54

60

66

Ω

7

7.

R

TT

 is the on-die termination resistance measured at V

TT

/2 of the GTL+ output driver.

COMP[1:0]

COMP Resistance

59.8

60.4

61

Ω

8

8.

COMP resistance must be provided on the system board with 1% resistors. COMP[1:0] resistors are to V

SS

.