How to Get the Most out of SDRAM

Every computer is a system, and even an old computer that still uses SDRAM can benefit from more or faster RAM. It's all about making sure the processor has the data it needs when it needs it.

Do Laptops Take the Same Modules as Desktops?

Although laptops do use the same memory chips as desktops, they do not use the same PC133 SDRAM DIMMs that you would find in a desktop. Part of the rationale for different form factors is that laptops simply don't have the interior room that desktops do. They are so much more space constrained that they need smaller memory modules. The other reason is that they don't need to support the all the features found in PC133 DIMMs. Servers use the same modules as desktops, so they need ECC memory; laptops don't and so non-ECC memory is standard, and that reduces the necessary pin count. Compare the two form factors:

  • DIMM: SDRAM is normally packaged in a 168-pin DIMM with two voltage notches. The package is 133.35 millimeters long and 30.48 millimeters high and uses 3.3 Volt signaling.
  • SO-DIMM: Laptop SDRAM is normally packaged in a 144-pin SO-DIMM with one voltage notch. This package is 67.6 millimeters long and 30 millimeters high. It also uses 3.3 Volt signaling.

How Do You Use PC133 in Your System?

RAM comes in several different forms, both electrically and physically. One advantage the industry has is that there is a standards body that ensures that each type of memory conforms to a codified body of specifications that ensures interoperability. In addition to SDRAM, there are also several different revisions of DDR and also RDRAM. Luckily, while each type of memory module is incompatible with other types, it's also fully compatible within its own type. Essentially, if it will fit, it will work. That being said, there are certain benefits to using PC133 SDRAM in systems that aim for lower speed SDRAM:

  • Stability: As a general rule, the more headroom a module has, the tighter timings it can run. This means that running PC133 on a PC100 motherboard will often give you better performance and stability than PC100 would. It's the same RAM with some small upgrades.
  • Overclocking: One notable point about synchronous memory is that when you overclock the processor, you overclock the RAM, too. This means that you either need more headroom on your RAM or to use higher specced memory than the system calls for. Replacing PC100 with PC133 is a simple way to get that headroom.

Using PC133 SDRAM

It's easy enough to use PC133, just snap a 256 MB 168-pin DIMM in the slot and you're away. All you have to do is make sure your motherboard supports that size module and that you're populating your slots correctly. It's not hard so long as you read the manual.