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Electrical Specifications

52 Intel

Itanium

Processor 9300 Series and 9500 Series Datasheet

2.6.5 Overshoot and Undershoot Guidelines

Overshoot (or undershoot) is the value of the maximum voltage above or below VSS.

The overshoot and undershoot specifications limit transitions beyond VCCIO or VSS due

to the fast signal edge rates. The processor can be damaged by single and/or repeated

overshoot or undershoot events on any input, output, or I/O buffer if the charge is

large enough (that is, if the overshoot or undershoot is great enough). Determining the

impact of an overshoot or undershoot condition requires knowledge of the magnitude,

the pulse duration, and the activity factor (AF). Permanent damage to the processor is

the likely result of excessive overshoot or undershoot.

2.6.5.1 Overshoot/Undershoot Magnitude, Pulse Duration and Activity Factor

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

reference level. For the Intel

Itanium

Processor 9300 Series and Intel

Itanium

Processor 9500 Series, both are referenced to VSS. It is important to note that

overshoot and undershoot conditions are separate and their impact must be

determined independently.

Pulse duration describes the total amount of time that an overshoot or undershoot

event exceeds the overshoot or undershoot reference voltage. Activity factor (AF)

describes the frequency of overshoot or undershoot occurrence relative to a clock.

Since the highest frequency of assertion of a single-ended signal is every other clock,

an AF = 1 indicates that the specific overshoot or undershoot waveform occurs every

other clock cycle. Thus, an AF = 0.01 indicates that the specific overshoot or

undershoot waveform occurs one time in every 200 clock cycles. The highest frequency

of assertion of any differential signal is every active edge of its associated clock (not

the reference clock). So, an AF = 1 indicates that the specific overshoot or undershoot

waveform occurs every cycle.

2.6.5.2 Overshoot/Undershoot Specifications

The overshoot and undershoot specifications listed in the following table specify the

allowable overshoot or undershoot for a single overshoot or undershoot event.

Table 2-25 specifies the maximum overshoot and undershoot for the Intel

Itanium

Processor 9300 Series, while Table 2-26 specifies the maximum overshoot and under-

shoot for the Intel

Itanium

Processor 9500 Series, respectively, identifying both the

single ended and the differential signalling pins. The overshoot and undershoot values

assume an activity factor of 100% and a pulse width of 25% over the signal pulse

width. The tables also include the absolute maximum and minimum values beyond

which the processor is not guaranteed to operate properly. These values assume a

pulse width of 1% and an activity factor of 100%.

2.6.5.2.1 Overshoot and Undershoot Specifications for the Intel

Itanium

Processor

9300 Series

Table 2-25. Overshoot and Undershoot Specifications For Differential

Intel

QuickPath Interconnect and Intel

SMI and Single-Ended Signals

for the Intel

Itanium

Processor 9300 Series (Sheet 1 of 2)

Symbol Parameter Min Max Unit

MAX-OS-SE

Overshoot for single-ended signals 1.45 V

MIN-US-SE

Undershoot for single-ended signals -0.247 V

ABSMAX-OS-SE

Absolute Max for single-ended signals 1.6 V

ABSMIN-US-SE

Absolute Min for single-ended signals -0.425 V