80546KF Datasheet, PDF (57/138 Pages) Intel Corporation – 64-bit Intel Xeon Processor MP with up to 8MB L3 Cache

Front Side Bus Signal Quality Specifications
3.1.4 Overshoot/Undershoot Pulse Duration
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.
Note: Oscillations below the reference voltage cannot be subtracted from the total overshoot/undershoot
pulse duration.
3.1.5
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. The highest frequency of assertion of any source synchronous signal is
every active edge of its associated strobe. So, an AF = 1 indicates that the specific overshoot (or
undershoot) waveform occurs every strobe cycle.
The specifications provided in Table 3-3 through Table 3-6 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 1: Activity factor for common clock AGTL+ signals is referenced to BCLK[1:0] frequency.
Note 2: Activity factor for source synchronous (2x) signals is referenced to ADSTB[1:0]#.
Note 3: Activity factor for source synchronous (4x) signals is referenced to DSTBP[3:0]# and
DSTBN[3:0]#.
3.1.6
Reading Overshoot/Undershoot Specification Tables
The overshoot/undershoot specification for the processor 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 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 that particular signal falls into. For AGTL+ signals operating in
the 4x source synchronous domain, use Table 3-3. For AGTL+ signals operating in the 2x
source synchronous domain, use Table 3-4. If the signal is an AGTL+ signal operating in the
common clock domain, use Table 3-5. Finally, all other signals are referenced in Table 3-6.
2. Determine the magnitude of the overshoot or the undershoot (relative to V_SS).
3. Determine the activity factor (how often does this overshoot occurs).
64-bit Intel^® Xeon™ Processor MP with up to 8MB L3 Cache Datasheet
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