Intel Celeron Processor in the 478-Pin Package at 1.80 GHz Datasheet

44 Datasheet
Intel
®
Celeron
®
Processor in the 478-Pin Package
3.2.1.3 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.
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.
The specifications provided in Table 22 through Table 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).
Notes:
1. Activity factor for AGTL+ signals is referenced to BCLK[1:0] frequency.
2. Activity factor for source synchronous (2x) signals is referenced to ADSTB[1:0]#.
3. Activity factor for source synchronous (4x) signals is referenced to DSTBP[3:0]# and
DSTBN[3:0]#.
3.2.1.4 Reading Overshoot/Undershoot Specification Tables
The overshoot/undershoot specification for the Celeron processor in the 478-pin package 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. For AGTL+ signals operating in the
common clock domain, use Table 24. For AGTL+ signals operating in the 2x source
synchronous domain, use Table 23. For AGTL+ signals operating in the 4x source
synchronous domain, use Table 22. Finally, all other signals reside in the 33 MHz domain
(asynchronous GTL+, TAP, etc.) and are referenced in Table 25.
2. Determine the magnitude of the overshoot (relative to V
SS)
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.