Intel Celeron Processor in the 478-Pin Package at 1.80 GHz Datasheet

Datasheet 27

Intel

Celeron

Processor in the 478-Pin Package

2.11 AGTL+ System Bus Specifications

Routing topology recommendations may be found in the appropriate Platform Design Guide as

referenced in Table 1. Termination resistors are not required for most AGTL+ 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 (known as V

REF

in previous documentation).

Table 12 lists the GTLREF specifications. The AGTL+ reference voltage (GTLREF) should be

generated on the system board using high precision voltage divider circuits. It is important that the

system board impedance is held to the specified tolerance, and that the intrinsic trace capacitance

for the AGTL+ signal group traces is known and well-controlled. For more details on platform

design see the Platform Design Guide.

NOTES:

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

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

CC.

3. GTLREF should be generated from V

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

to Table 1 for the appropriate Platform Design Guide for implementation details.

4. R

is the on-die termination resistance measured at V

of the AGTL+ output driver. Refer to processor I/O

buffer models for I/V characteristics.

5. COMP resistance must be provided on the system board with 1% resistors. See the appropriate platform

design guide for implementation details.

6. The V

CC referred to in these specifications is the instantaneous VCC.

Table 12. AGTL+ Bus Voltage Definitions

Symbol Parameter Min Typ Max Units Notes

GTLREF

Bus Reference

Voltage

2/3 VCC - 2% 2/3 VCC

2/3 VCC + 2% V 2, 3, 6

Termination

Resistance

45 50 55 W 4

COMP[1:0]

COMP

Resistance

50.49 51 51.51 W 5