Intel III Xeon 733 MHz 80526KZ733256 Manuale Utente
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80526KZ733256
SIGNAL QUALITY
35
Overshoot/Undershoot is the absolute value of the maximum voltage differential across the input buffer relative to the
termination voltage (V
TT
). The overshoot/undershoot guideline limits transitions beyond VTT or VSS due to the fast signal
edge rates. The processor can be damaged by repeated Overshoot/Undershoot events on 1.5 V or 2.5 V tolerant buffers
if the potential is large enough (i.e., 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. The
Overshoot/Undershoot specifications apply to the processor, regardless of whether the processor is driving or receiving
the signal.
if the potential is large enough (i.e., 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. The
Overshoot/Undershoot specifications apply to the processor, regardless of whether the processor is driving or receiving
the signal.
4.2.3.1 Overshoot/Undershoot Magnitude
Overshoot magnitude describes the maximum potential difference between a signal and its reference voltage level, Vss.
Undershoot Magnitude describes the maximum potential difference between a signal and V
Overshoot magnitude describes the maximum potential difference between a signal and its reference voltage level, Vss.
Undershoot Magnitude describes the maximum potential difference between a signal and V
TT
(undershoot). While
overshoot can be measured relative to VSS using one probe (probe on signal and ground lead on VSS), Undershoot must
be measured relative to V
be measured relative to V
TT
. This can be accomplished by simultaneously measuring the V
TT
plane while measuring the
signal undershoot. The true waveform can then be calculated by the oscilloscope itself or by the following oscilloscope
data file analysis:
data file analysis:
Converted Undershoot Waveform = V
TT
- Signal
Note: This Converted Undershoot Waveform appears as a positive (overshoot) signal.
Note: Overshoot (rising edge) and Undershoot (falling edge) conditions are separate and their impact must be
determined independently.
After the conversion, the Overshoot/Undershoot Specifications can be applied to the Converted Undershoot Waveform
using the Overshoot/Undershoot Magnitude and Pulse Duration Specifications in Tables 23, 24 and 25.
Overshoot/Undershoot Magnitude levels must also observe the Absolute Maximum Specifications. 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 Durations. Provided that the magnitude of the Overshoot/Undershoot is within
the Absolute Maximum Specifications, the impact of the Overshoot/Undershoot Magnitude may be determined based
upon the Pulse Duration and Activity Factor.
4.2.3.2 Overshoot/Undershoot Pulse Duration
Overshoot/Undershoot Pulse Duration describes the total time that an Overshoot/Undershoot event exceeds the
Overshoot/Undershoot Reference Voltage (Vos_ref = 1.635V). This total time could encompass several oscillations
above the Overshoot/Undershoot Reference Voltage. Thus, multiple Overshoot/Undershoot pulses within a single
Overshoot/Undershoot event must be measured to determine the total Pulse Duration.
Note: Oscillations below the Reference Voltage cannot be subtracted from the total Overshoot/Undershoot Pulse
Duration.
Note: Multiple Overshoot/Undershoot events occurring within the same clock cycle must be considered together as one
event. Using the worst-case Overshoot/Undershoot Magnitude, sum together the individual Pulse Durations to determine
the total Overshoot/Undershoot Pulse Duration for that total event.
Overshoot/Undershoot Pulse Duration describes the total time that an Overshoot/Undershoot event exceeds the
Overshoot/Undershoot Reference Voltage (Vos_ref = 1.635V). This total time could encompass several oscillations
above the Overshoot/Undershoot Reference Voltage. Thus, multiple Overshoot/Undershoot pulses within a single
Overshoot/Undershoot event must be measured to determine the total Pulse Duration.
Note: Oscillations below the Reference Voltage cannot be subtracted from the total Overshoot/Undershoot Pulse
Duration.
Note: Multiple Overshoot/Undershoot events occurring within the same clock cycle must be considered together as one
event. Using the worst-case Overshoot/Undershoot Magnitude, sum together the individual Pulse Durations to determine
the total Overshoot/Undershoot Pulse Duration for that total event.
4.2.3.3 Overshoot/Undershoot Activity Factor
Activity Factor (AF) describes the frequency of Overshoot/Undershoot occurrence relative to a Clock. Since the highest
frequency of assertion of an AGTL+ or a CMOS signal is every other clock, an AF = 1 indicates that the specific
Overshoot or Undershoot waveform occurs EVERY OTHER clock cycle (e.g., 1-0-1-0… system bus switching pattern).
Thus, an AF = 0.01 indicates that the specific Overshoot or Undershoot waveform occurs 1 time in every 200 CLK cycles.
The specifications provided in Tables 23, 24 and 25 show 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 < 1, means that there
can be NO other Overshoot/Undershoot events, even of lesser Magnitude (note that if AF = 1, then the event occurs at all
times and no other events can occur).
Note: Activity Factor for AGTL+ signals is referenced to BCLK frequency.
Note: Activity Factor for CMOS signals is referenced to PICCLK frequency.
Activity Factor (AF) describes the frequency of Overshoot/Undershoot occurrence relative to a Clock. Since the highest
frequency of assertion of an AGTL+ or a CMOS signal is every other clock, an AF = 1 indicates that the specific
Overshoot or Undershoot waveform occurs EVERY OTHER clock cycle (e.g., 1-0-1-0… system bus switching pattern).
Thus, an AF = 0.01 indicates that the specific Overshoot or Undershoot waveform occurs 1 time in every 200 CLK cycles.
The specifications provided in Tables 23, 24 and 25 show 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 < 1, means that there
can be NO other Overshoot/Undershoot events, even of lesser Magnitude (note that if AF = 1, then the event occurs at all
times and no other events can occur).
Note: Activity Factor for AGTL+ signals is referenced to BCLK frequency.
Note: Activity Factor for CMOS signals is referenced to PICCLK frequency.
4.2.3.4 Determining if a System Meets the Overshoot/Undershoot Specifications