Datasheet

24 Dual-Core Intel
®
Itanium
®
Processor 9000 and 9100 Series Datasheet
Electrical Specifications
2.5.2 Overshoot/Undershoot Pulse Duration
Pulse duration describes the total time that an overshoot/undershoot event exceeds the
overshoot/undershoot reference voltage (V
CTERM
/GND). 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.
2.5.3 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 (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 other
strobe cycle. The specifications provided in Table 2-14 through Table 2-17 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 (if AF = 1, then the event occurs at all
times and no other events can occur).
Note: AF for the common clock AGTL+ signals is referenced to BCLKn, and BCLKp frequency.
The wired-OR Signals (BINIT#, HIT#, HITM#, BNR#, TND#, BERR#) are common
clock AGTL+ signals.
Note: AF for source synchronous (2x) signals is referenced to STBP#[7:0], and STBN#[7:0].
2.5.4 Reading Overshoot/Undershoot Specification Tables
The overshoot/undershoot specification for the processor is not a simple single value.
Instead, many factors are needed in order to correctly interpret the overshoot/
undershoot specification. In addition to the magnitude of the overshoot, the following
parameters must also be known: the width of the overshoot and the AF. To determine
the allowed overshoot for a particular overshoot event, the following must be done:
1. Determine the signal group that the particular signal falls into. For AGTL+ signals
operating in the 2x source synchronous domain, use Table 2-14 through
Table 2-16. If the signal is a wired-OR AGTL+ signal operating in the common clock
domain, use Table 2-15 through Table 2-17.
2. Determine the magnitude of the overshoot, or the undershoot (relative to GND).
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. The pulse duration shown in the table refers to
the period where either the maximum overshoot (for high phase) and undershoot
(for low phase) occurred.