It is a test board consisting of clock generator and buffer 4 of the buffered signal go to the DIMM socket while other clock signal go to a reference net. Clock delay and skew can be measured at the SDRAM chips on the module and then compared against the signal at the reference net.
It is for module design verification. It is the supplier’s quality standard to ensure consistent performance. It is an industry reference standard. It allows the tuning of PLL feed back on the module to balance the module timing. It is also an accepted JEDEC industry standard.
It is very easy to use. All you have to do is to connect an external power supply and 2 oscilloscope probes on it. You then turn it on and compare the signal time delay between the 2 signals. Depending on the skew of the clock signals, you will either tune the feedback of the PLL or change the clock loading to balance the skew.
Although this board was designed by IBM; Manufacturing, sales, distribution and after service support is solely responsible by CST, Inc. Call CST, Inc. at (972) 241-2662 for any concern on this product
This Clock Reference Board covers PC100 unbuffered modules, and PC133 registered modules. It has built-in regular clock or spread-spectrum mode. It is built with controlled impedance PC board for tightest performance tolerance. It has a separate Vcc plane that can be used for voltage shmooing test. It has extensive synthesizer de-coupling to assure stability. It also has marked test point for ease of use. All boards are built as one batch against a “golden board” to ensure consistency.
CST, Inc. provides one full year warranty on the Clock Reference Board. Warranty includes parts and labor except the DIMM socket, which considered as a consumable part. Contact (972) 241-2662 for an RMA number.
This Clock Reference Board was designed and tested for the PC100 unbuffered module as well as for the PC133 registered modules. Due to the late release of the PC133 unbuffered DIMM specification, this design cannot guarantee its performance on PC133 unbuffered modules
The Clock Reference Board is intended to be a standard clock timing reference standard. It is not intended nor designed as a memory DIMM tester. However, CST, Inc. does provide full line of DIMM tester that will test most any type of module on the market.
All scope probes has capacitance that can affect the measurement (load down effect). Although a standard 10X probe can do the proper measurement, we do recommend you use an active scope probe that has less than 1pf capacitance loading. In any case, a probe calibration should be performed to cancel out the variation factor from one probe to the other.
The higher bandwidth of the oscilloscope and the less loading of the scope probe will minimize the noise display on the oscilloscope. That is why we recommend the TDS11081C scope and the 1pf active probe.
Although the Clock Reference Board uses a power connector very similar to the standard ATX type power supply, the required voltage is totally different from the ATX power supply. Instead, it requires 3.3Vdc and 2.5Vdc, which are not provided by the ATX power supply. Care should be taken to supply the power from bench power supplies that can be set to the 3.3V and the 2.5V.
The power supply capacity is not a major issue. You should use any bench power supply like B&K, HP…etc. In any case, make sure it is adjusted to 3.3V and 2.5V before connecting or turning on the system
The Clock Reference Board was designed and simulated to be within 100ps of tolerance. Prototype verification on several boards result in variation of 40ps between boards. CST, Inc. does guarantee 100ps tolerance from board to board.