Intel E5-1660 BX80621E51660 User Manual

Intel® Xeon® Processor E5-1600/E5-2600/E5-4600 Product Families

185

Datasheet Volume One

Overshoot/undershoot pulse duration describes the total amount of time that an 
overshoot/undershoot event exceeds the overshoot/undershoot reference voltage. The 

total time could encompass several oscillations above the reference voltage. Multiple 
overshoot/undershoot pulses within a single overshoot/undershoot event may need to 

be measured to determine the total pulse duration.

Oscillations below the reference voltage cannot be subtracted from the total overshoot/

undershoot pulse duration.

Activity factor (AF) describes the frequency of overshoot (or undershoot) occurrence 
relative to a clock. Since the highest frequency of assertion of any common clock signal 

is every other clock, an AF = 0.1 indicates that the specific overshoot (or undershoot) 

waveform occurs every other clock cycle.

The specification provided in the table shows the maximum pulse duration allowed for a 

given overshoot/undershoot magnitude at a specific activity factor. Each table entry is 

independent of all others, meaning that the pulse duration reflects the existence of 
overshoot/undershoot events of that magnitude ONLY. A platform with an overshoot/

undershoot that just meets the pulse duration for a specific magnitude where the AF < 

0.1, means that there can be no other overshoot/undershoot events, even of lesser 
magnitude (note that if AF = 0.1, then the event occurs at all times and no other 

events can occur).

The overshoot/undershoot specification for the processor is not a simple single value. 

Instead, many factors are needed to determine the over/undershoot specification. In 

addition to the magnitude of the overshoot, the following parameters must also be 
known: the width of the overshoot and the activity factor (AF). To determine the 

allowed overshoot for a particular overshoot event, the following must be done:

1. Determine the signal group a particular signal falls into. 
2. Determine the magnitude of the overshoot or the undershoot (relative to VSS).
3. Determine the activity factor (How often does this overshoot occur?). 
4. Next, from the appropriate specification table, determine the maximum pulse 

duration (in nanoseconds) allowed.

5. Compare the specified maximum pulse duration to the signal being measured. If 

the pulse duration measured is less than the pulse duration shown in the table, 
then the signal meets the specifications.

Undershoot events must be analyzed separately from overshoot events as they are 

mutually exclusive.

The overshoot/undershoot specifications listed in the table specify the allowable 

overshoot/undershoot for a single overshoot/undershoot event. However most systems 

will have multiple overshoot and/or undershoot events that each have their own set of 
parameters (duration, AF and magnitude). While each overshoot on its own may meet