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SIMCHECK Application Note


Version 1.47, or higher, for Sync DIMMCHECK 168 can now determine if a tested module is a PC133, 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 PC133 standard was developed by a group of companies led by Via Technologies, IBM Microelectronics, Micron Semiconductor, NEC and Samsung. It is essentially based on the INTEL PC-100 specification with the enhancement of 133MHz operation at a Cas Latency of 3 (CL=3) and access time from clock (Tac) of 5.4nS. Accordingly, the SPD data of a PC133 modules is similar to the PC-100 SPD data, with the exception of byte 9 (SDRAM device cycle time CL=3) set to 75h (7.5nS) and byte 10 (SDRAM device access time from clock at CL=3) set to 54h (5.4nS). Please review Application Note INN-8558-APN12 for more information.

The algorithm for determining PC133 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 PC133 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 PC133 tests. Since the PC133 tests are conducted only on modules that have been detected as "at least" PC-100, a full understanding of our PC-100 determination is essential to understand our PC133 determination. Please refer to Application Notes INN-8558-APN13 and INN-8558-APN14 regarding the measurement for the Tac values, and the important factors for detecting PC-100 modules.


The following are examples of the first summary screen on SIMCHECK following the end of Basic Test of a PC-133 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 Screen Image

The display of PC-133 compliance appears on the second line of the screen, and it has the header "TEST=" followed by "PC-133 RANGE" if SIMCHECK determines that the module within PC-133 specifications.

The third line indicates "PAGE BURST= xxMHz" indicating the maximum page burst of the tested module. The fourth line in this example indicates "SPD=JEDEC PC133" which indicates that the data in the SPD claims the module to be a PC-133.

Determination of PC133 is performed at the start of BASIC TEST, once SIMCHECK detects that the module under test meets the PC-100 requirements. At that point, the unit SPD is checked for PC133 compliance.

Afterwards, the fast access time from clock at CL=3 is determined. If the module can then work at 133MHz, the tester will determine that it is PC133, showing the speed 133MHz during BASIC TEST and indicating a Tac range of PC133 during the summary screen and in the test log.

Screen Image Screen Image

Since PC133 is a subset of the PC-100 specification, the Extensive Test currently continues at 100MHz. Currently you can achieve continuous 133MHz test during BASIC Test and EXTENSIVE Test using the Frequency Setup or the Change-on-the-Fly features.

Screen Image

Version 1.47 is the first to support automatic PC133 detection and it does not use all the recently introduced features in the Sync DIMMCHECK 168 engine. Future versions will utilize more of these test features to further enhance the PC133 detection.


If your tester consistently fails to detect the PC133 module, various upgrades and a calibration may be required, depending on its production version. Obviously, units manufactured in 1997 and early 1998 (Sync DIMMCHECK 168 PCB Ver. C) require more changes than later units.

We recommend that your SIMCHECK II/IIse PLUS be sent for a "CALIBRATION & HARDWARE UPGRADES at our factory (Houston, Texas) every 12-18 months.

IMPORTANT NOTE: The BASIC Test is the only test used by SIMCHECK II to determine PC133 compliance. It provides an information summary that gives specific information if the module is PC133 compliant. Other frequencies are used throughout the Extensive Test to create additional conditions for the test. Therefore, if a module finishes BASIC Test as PC133, the fact that it may run at 100MHz during Extensive Test or AUTO LOOP does not mean that the module is not a PC133.

An exact measurement and full certification of a module as PC-133 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-133. However, 100% accuracy is beyond the scope of this inexpensive tester.

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