Intel Pentium 4 (551) JM80547PG0961MM User Manual
Product codes
JM80547PG0961MM
Intel
®
Pentium
®
4 Processor in the 423-pin Package
34
When performing simulations to determine impact of overshoot and undershoot, ESD diodes must
be properly modelled. ESD protection diodes do not act as voltage clamps and will not provide
overshoot or undershoot protection. ESD diodes modelled within Intel I/O buffer models do not
clamp undershoot or overshoot and will yield correct simulation results. If other I/O buffer models
are being used to characterize the Pentium 4 processor system bus, care must be taken to ensure
that ESD models do not clamp extreme voltage levels. Intel I/O buffer models also contain I/O
capacitance characterization. Therefore, removing the ESD diodes from an I/O buffer model will
impact results and may yield excessive overshoot/undershoot.
be properly modelled. ESD protection diodes do not act as voltage clamps and will not provide
overshoot or undershoot protection. ESD diodes modelled within Intel I/O buffer models do not
clamp undershoot or overshoot and will yield correct simulation results. If other I/O buffer models
are being used to characterize the Pentium 4 processor system bus, care must be taken to ensure
that ESD models do not clamp extreme voltage levels. Intel I/O buffer models also contain I/O
capacitance characterization. Therefore, removing the ESD diodes from an I/O buffer model will
impact results and may yield excessive overshoot/undershoot.
3.3.2
Overshoot/Undershoot Magnitude
Magnitude describes the maximum potential difference between a signal and its voltage reference
level. For the Pentium 4 processor both overshoot and undershoot are referenced to V
level. For the Pentium 4 processor both overshoot and undershoot are referenced to V
SS
. It is
important to note that overshoot and undershoot conditions are separate and their impacts must be
determined independently.
determined independently.
Overshoot/undershoot magnitude levels must observe the absolute maximum specifications listed
in Table 18 through Table 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 durations. Provided that the magnitude of the overshoot/undershoot is within the
absolute maximum specifications (2.3V for overshoot and -0.65V for undershoot), the pulse
magnitude, duration and activity factor must all be used to determine if the overshoot/undershoot
pulse is within specifications.
in Table 18 through Table 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 durations. Provided that the magnitude of the overshoot/undershoot is within the
absolute maximum specifications (2.3V for overshoot and -0.65V for undershoot), the pulse
magnitude, duration and activity factor must all be used to determine if the overshoot/undershoot
pulse is within specifications.
3.3.3
Overshoot/Undershoot Pulse Duration
Pulse duration describes the total time 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.
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.
Note 1: Oscillations below the reference voltage cannot be subtracted from the total overshoot/
undershoot pulse duration.
undershoot pulse duration.
3.3.4
Activity Factor
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 = 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.
clock. Since the highest frequency of assertion of any common clock 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.
For source synchronous signals (address, data, and associated strobes), the activity factor is in
reference to the strobe edge, since the highest frequency of assertion of any source synchronous
signal is every active edge of its associated strobe. An AF = 1 indicates that the specific overshoot
(or undershoot) waveform occurs every strobe cycle.
reference to the strobe edge, since the highest frequency of assertion of any source synchronous
signal is every active edge of its associated strobe. An AF = 1 indicates that the specific overshoot
(or undershoot) waveform occurs every strobe cycle.
The specifications provided in Table 18 through Table 21 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
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