PC133 SDRAM Roundup - April 2000

Now that we’ve established that there is a need for PC133 SDRAM let’s take a quick look at what makes a good module in the first place.

When Intel introduced the PC100 SDRAM specification in 1998 they put together a list of issues that needed to be addressed by both the chip and module manufacturers in order for the specification to be successful.  That list included the following:

• Minimum and maximum trace lengths for all signals on the module
• Precise specifications for trace width and spacing
• 6 layer PCB's with unbroken power and ground planes
• Detailed specifications for the distances between each circuit board layer
• Precisely matched clock trace lengths, as well as routing, loading, and termination requirements
• Series termination resistors on the data lines
• Detailed SDRAM component specification
• Detailed EEPROM programming specification
• Special Marking Requirements
• ElectroMagnetic Interference Suppression
• Selectively gold plated printed circuit boards

The actual specification goes into great depth for each one of those points, spelling out  exactly what the manufacturer must do in order to properly meet the specification.  Ideally this works out just fine because as long as you have a manufacturer that follows these specifications perfectly all SDRAM should be created equal and there shouldn’t be any question as to exactly how far your SDRAM will go when overclocking.

Unfortunately, the fact of the matter is that most of the SDRAM you can go out and buy features chips made by one manufacturer, a PCB made by another manufacturer, and is assembled at a third party plant. 

This brings out the point we have made in our past SDRAM roundups, that there are two parts to the equation used to make a quality DIMM: the SDRAM chips themselves and the PCB.  Both parts of this equation carry an equal weight, meaning that if you have some very high performing and ultra reliable SDRAM chips on a poorly manufactured PCB your module is most likely not living up to its true potential.

This is the reason that you can find SDRAM modules with identical labels on the individual chips themselves, but that can reach completely different frequencies simply because of differences in the manufacturing of their PCBs and the trace layouts on the boards as well. 

Since heat does not play a major factor in the overclockability of SDRAM modules, it is generally safe to say that although your mileage may vary from one module to the next, it isn’t as likely to vary as something like the overclocking potential of a CPU.