Intel Pentium 4 Processor in the 478-PinPackage at 1.40 GHz, 1.50 GHz, 1.60 GHz, 1.70 GHz, 1.80 GHz, 1.90 GHz, and 2GHz

System Bus Signal Quality Specifications

42 Datasheet

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 in the 478-pin package both are referenced

to V

. It is important to note that overshoot and undershoot conditions are separate and

their impact must be determined independently.

Overshoot/undershoot magnitude levels must observe the absolute maximum

specifications listed in Table 22 through Table 25 . 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 (maximum overshoot = 2.3 V, maximum

undershoot = -0.65 V). 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 can not be subtracted from the total

overshoot/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.

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 Ta ble 22 through Ta b le 2 5 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 AGTL+ signals is referenced to BCLK[1:0] frequency.

Note 2: Activity factor for source synchronous (2x) signals is referenced to ADSTB[1:0]#.