Intel Itanium 2 Processor 2.5 System Bus Signal Quality Specifications and Measurement Guidelines

Datasheet 23

Electrical Specifications

2.5 System Bus Signal Quality Specifications and Measurement Guidelines

Overshoot (or undershoot) is the absolute value of the maximum voltage above the nominal

VCTERM voltage (or below GND), as shown in Tabl e 2-3. The overshoot/undershoot specifications

limit transitions beyond VCTERM or GND due to the fast signal edge rates. The processor can be

permanently damaged by repeated overshoot or undershoot events on any input, output, or I/O

buffer if the charge is large enough (that is, if the overshoot/undershoot is great enough).

Determining the impact of an overshoot/undershoot condition requires knowledge of the

magnitude, the pulse duration, and the activity factor (AF).

Magnitude describes the maximum potential difference between a signal and its voltage reference

level. For the Itanium 2 processor, both are referenced to GND as shown in Figure 2-3. It is

important to note that overshoot and undershoot conditions are separate and their impact must be

determined independently. Overshoot/undershoot magnitude levels must observe the absolute

maximum specifications listed in Table 2 -13 through Table 2-21. These specifications must not be

violated at any time regardless of bus activity or system state. Within these specifications are

threshold levels that define different allowed pulse duration. Provided that the magnitude of the

overshoot/undershoot is within the absolute maximum specifications (1.8 V for overshoot and

–0.60 V fo r undershoot), the pulse magnitude, duration and activity factor must all be used to

determine if the overshoot/undershoot pulse is within specifications.

Vin, SMBus SMBus Buffer DC Input Voltage with

Respect to GND –0.1 6.0 V 4

Vin, AGTL+ AGTL+ Buffer DC Input Voltage with

Respect to GND –0.1 1.9 V 5, 6

VCTERM Any VCTERM Voltage with Respect to

GND –0.1 1.9 V 3

Vin,TAP TAP Buffer DC Input Voltage with

Respect to GND. –0.1 2.1 V 5

NOTES:

1. Storage temperature is temperature in which the processor can be stored for up to one year.

2. Shipping temperature is temperature in which the processor can be shipped for up to 24 hours.

3. See Table2-4 through Table2-9 inclusive for operating voltages.

4. Parameters are from third party vendor specifications.

5. Maximum instantaneous voltage at receiver buffer input.

6. Specification includes Vin,AGTL+ and Vin,AGTL+ ASYNCHRONOUS (AGTL+ asynchronous buffer DC input voltage with

respect to GND.

Table 2-12. Itanium® 2 Processor Absolute Maximum Ratings (Sheet 2 of 2)

Symbol Parameter Minimum Maximum Unit Notes