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

Datasheet 43

Note 3: Activity factor for source synchronous (4x) signals is referenced to DSTBP[3:0]#

and DSTBN[3:0]#.

3.3.5 Reading Overshoot/Undershoot Specification Tables

The overshoot/undershoot specification for the Pentium 4 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 Tab le 2 4. For AGTL+ signals operating in the 2x

source synchronous domain, use Tab le 2 3. For AGTL+ signals operating in the 4x

source synchronous domain, use Tab le 2 4. Finally, all other signals reside in the

33MHz domain (asynchronous GTL+, TAP, etc.) and are referenced in Table 25.

2. Determine the magnitude of the overshoot (relative to V

)

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.

3.3.6 Determining if a System Meets the Over/Undershoot Specifications

The overshoot/undershoot specifications listed in the following tables specify the

allowable overshoot/undershoot for a single overshoot/undershoot event. However most

systems will have multiple overshoot and/or undershoot events that each have their own

set of parameters (duration, AF and magnitude). While each overshoot on its own may

meet the overshoot specification, when you add the total impact of all overshoot events,

the system may fail. A guideline to ensure a system passes the overshoot and undershoot

specifications is shown below. Results from simulation may also be evaluated by utilizing

the Intel® Pentium® 4 Processor in the 478-pin Package Overshoot Checker through the

use of time-voltage data files.

1. Ensure no signal ever exceeds V

CC_MAX

or -0.25V OR

2. If only one overshoot/undershoot event magnitude occurs, ensure it meets the over/

undershoot specifications in the following tables OR

3. If multiple overshoots and/or multiple undershoots occur, measure the worst case

pulse duration for each magnitude and compare the results against the AF = 1

specifications. If all of these worst case overshoot or undershoot events meet the

specifications (measured time < specifications) in the table (where AF=1), then the

system passes.