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SIMCHECK Application Note


Version 1.40, or higher, for Sync DIMMCHECK 168 can now determine if a tested module is a PC-100, based on several actual measurements and a smart algorithm that takes into account the actual resolutions of the measurements of our test system. This application note further explains the measurement and the results shown by the test summary screens and in the Test Log.

The algorithm for determining PC-100 compliance uses various measurements made by the tester during the Basic Test. In particular, it uses information from maximum page burst frequency, frequency drift during test, the Tac measurements for CAS Latency 3 and 2, and the SPD data. It also allows for future enhancements when additional measurements will be available as our R&D efforts proceed.

The algorithm is a simplified Expert System, as it sometimes needs to judge between conflicting measurements. Therefore, our test summary screens (as well as the Test Log) provide a determination of PC-100 compliance AND some of the results that led to that conclusion. Advanced users can further look at the results and determine the margin or accuracy of the SIMCHECK determination.

This application note provides the details for our PC-100 reports. Please also refer to Application Note INN-8558-APN13 regarding the measurement for the Tac values, which comprise an important factor for PC-100 determination.


The following is an example of the first summary screen on SIMCHECK following the end of Basic Test of a PC-100 module. Alternatively, you can reach this screen even before the end of Basic Test if you abort the test by pressing F5 during Basic Test:

Screen Image

The determination of the PC-100 compliance appears on the second line of the screen and it has the header "TEST=" followed by "PC-100" if SIMCHECK determines that the module is PC-100.

The third line indicates "PAGE BURST=100MHz" and it indicates that the maximum page burst of the tested module was 100MHz. The fourth line in this example indicates "SPD=INTEL PC-100" which indicates that the data in the SPD claims the module to be a PC-100.

The next example shows the first summary screen of a PC-66 module:

Screen Image

The message "TEST=PC-66" indicates that SIMCHECK has determined that the module is a PC-66. You can see that the bottom line also verifies that the SPD claims the module to be a PC-66.

The third example shows a module that is marked as PC-66 by the SPD, but SIMCHECK determines that the module matches the speed of other PC-100 modules:

Screen Image

The message "TEST=PC-100 RANGE" is indicating that the module indeed ran at 100MHz, even though the SPD data shows "SPD=INTEL PC-66". The maximum page burst in this example was 112MHz.

The first summary screen is followed by the Tac measurement screen as in the following examples:

Screen Image Screen Image

Please refer to Application Note INN-8558-APN13 for further details about these measurements.


An exact measurement and full certification of a module as PC-100 requires the use of a very expensive tester with a variable temperature oven, sub-nanosecond accuracy, and complex capabilities to compensate for all loading effects. SIMCHECK II and the Sync DIMMCHECK have an inherent inaccuracy of about +/-1 nS in determining the Tac measurements. The patent pending page bursting mechanism of the Sync DIMMCHECK provides a fairly accurate measurement of the maximum frequency in which the tested module can burst. By using an Expert System that gives a certain weight for each tested parameter, we are able to provide a close overall determination as to whether the module is PC-100 or PC-66. However, 100% accuracy is beyond the scope of this inexpensive tester.

If a PC-100 module is identified as PC-66, you can further investigate the measurements and see what margin of error exists.

If a PC-66 module is identified as "PC-100 RANGE", please note the module may or may not work in motherboards that require strict PC-100 compliance. This is why we use the RANGE notation.

IMPORTANT NOTE: The BASIC Test is the only test used by SIMCHECK II to determine PC-100 compliance. It provides an information summary that gives specific information if the module is PC-100 compliant. Other frequencies are used throughout the Extensive Test to create additional conditions for the test. Therefore, if a module finishes BASIC Test as PC-100, the fact that it may run at 83MHz during Extensive Test or AUTO LOOP does not mean that the module is not a PC-100.

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