DIMM vs SO-DIMM: Characteristics, Definition and Differences

When we talk about RAM oriented to the consumer (we, the users), we can find it in two different formats: either in DIMM format, which is the usual “full size” that we see on desktop PCs, or in the SO- format. DIMM, smaller and oriented to laptops and mini PCs . In this article we are going to tell you the differences between RAM DIMM vs SO-DIMM , and why laptops and mini PCs use RAM of this second type.

Although there are some rare exceptions, it is normal that all desktop PCs only support RAM in DIMM format, while for laptops, the type of memory supported is SO-DIMM. Why is it like this?

DIMM vs SO-DIMM

RAM DIMM vs SO-DIMM: physical differences

RAM in SO-DIMM format is named after the English acronym for ” Small Outline Dual In-line Memory Module” , and it is precisely those words “Small Outline” that differentiates them from common DIMMs. Precisely, the difference is merely physical, since the modules in SO-DIMM format were designed precisely to take up less space and thus be able to be used in small equipment such as laptops.

Memoria RAM DIMM vs SO-DIMM

Given the physical differences in size between the two types of RAM modules, there are obviously also differences in the socket of the motherboard where they are installed and, therefore, also in their connections. Thus, logically depending on the generation of the memory module, they will have a number of pins or others. You can see it in the following table.

Memory type DIMM SO-DIMM
SDR memory type DIMM 168 pins SO-DIMM 100/144 pins
DDR memory type DIMM 184 pins SO-DIMM 200 pin
DDR2 memory type DIMM 240 pins SO-DIMM 200 pin
DDR3 memory type DIMM 240 pins SO-DIMM 204 pins
DDR4 memory type DIMM 288 pins SO-DIMM 260 pins

Not surprisingly, modules in DIMM format always have more contacts than SO-DIMMs, taking advantage of the fact that they are considerably longer. This allows that, even with the same technical specifications, the DIMM modules always have greater margins for overclocking, as well as for having higher memory densities (we repeat, even with the same characteristics, the greater physical size allows for greater margins).

Why don’t they make laptops with DIMM memory?

The reason is basically for the use of space. When you are designing a laptop you want to make the most of the space you have to be able to integrate the best possible hardware while occupying the minimum space, since the premise of laptops is that they are precisely portable in the sense of being able to carry them easily and comfortably. from one place to another, and that implies that they are small, thin and light.

Integrating RAM memory in SO-DIMM format facilitates this task, which, although not essential, does help to comply with this premise. In addition to being smaller and narrower, SO-DIMMs have sockets that allow them to be installed horizontally, while the sockets of normal DIMMs are considerably thicker and putting them horizontally would mean having to install a sisterboard on the motherboard. of the laptop, something that would not be too viable (although there have been cases in which they have done so).

Although it is true that they could implement a viable method to be able to install DIMMs in a laptop in the same way, why do it having SO-DIMMs?