Pentium® III Processor for the PGA370 Socket at 500 MHz to 866 MHz
3.3.5
Reading Overshoot/Undershoot Specification Tables
The overshoot/undershoot specification for the Pentium III processor for the PGA370 socket is not
a simple single value. Instead, many factors are needed to determine what the over/undershoot
specification is. In addition to the magnitude of the overshoot, the following parameters must also
be known: the junction temperature the processor will be operating at, the width of the overshoot
(as measured above 1.635V) 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 that particular signal falls into. If the signal is an AGTL+ signal
operating with a 100 MHz system bus, use Table 20 (100MHz AGTL+ signal group). If the
signal is an AGTL+ signal operating with a 133MHz system bus, use Table 21 (133 MHz
AGTL+ signal group). If the signal is a CMOS signal, use Table 22 (33 MHz CMOS signal
group).
2. Determine the maximum junction temperature (Tj) for the range of processors that the system
will support (80oC or 85oC).
3. Determine the Magnitude of the overshoot (relative to VSS)
4. Determine the Activity Factor (how often does this overshoot occur?)
5. From the appropriate Specification table, read off the Maximum Pulse Duration (in ns)
allowed.
6. 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.
The above procedure is similar for undershoots after the undershoot waveform has been converted
to look like an overshoot. Undershoot events must be analyzed separately from Overshoot events
as they are mutually exclusive.
Below is an example showing how the maximum pulse duration is determined for a given
waveform.
Table 19. Example Platform Information
Required Information
Maximum Platform Support
Notes
FSB Signal Group
Max Tj
133 MHz AGTL+
85 °C
Overshoot Magnitude
2.13V
Measured Value
Measured overshoot occurs on
average every 20 clocks
Activity Factor (AF)
0.1
NOTES:
1. Corresponding Maximum Puse Duration Specification - 2.4 ns
2. Pulse Duration (measured) - 2.0 ns
Given the above parameters, and using Table 21 (85 oC/AF = 0.1 column) the maximum allowed
pulse duration is 2.4 ns. Since the measure pulse duration is 2.0 ns, this particular overshoot event
passes the overshoot specifications, although this doesn't guarantee that the combined overshoot/
undershoot events meet the specifications.
38
Datasheet
INTEL [ INTEL ]
