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Once your laptop loses oomph, it’s often that the cause is low system memory. You’ve likely heard that modern laptop memory upgrades come in the form of a laptop SODIMM, but just what are they, and perhaps most importantly, how can you buy the one right for your laptop? To save you confusion, let’s go over the vital aspects you should know before clicking the order button!

What is a laptop SODIMM?

A laptop SODIMM is the shorthand term for laptop Small Outline Dual Inline Memory Module. Quite a mouthful wouldn’t you think? Fortunately, a SODIMM is rather small and is the name given to the PCB (Printed Circuit Board) on which modern laptop memory is sold.

Consequently, each time you stumble across a laptop memory upgrade, it’s very likely to be a laptop SODIMM of some sort. Does this mean all laptop SODIMM’s are identical? Unfortunately not, but luck has it that it’s not as complicated as it sounds.

Laptop SODIMM’s differ depending on what type of memory they feature. Older SDRAM SODIMM’s for example are 144pin, slightly newer DDR and DDR2 SODIMM’s are 200pin while the currently latest DDR3 SODIMM’s are 204pin. Their physical dimensions also vary but ever so slightly.

The main thing to remember is that laptop SODIMM’s of varying types can’t be mixed together in the same laptop. For example, if your laptop uses DDR3 memory then there’s no use trying to install a DDR2 SODIMM in there. It’s not merely the number of pins that vary but also the pin layout, operating voltage, timings and addressing etc.

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Does this mean upgrading is a burden best left to professionals? Of course not!

Laptop SODIMM compatibility

While it’s impossible to mix and match SDRAM, DDR, DDR2 or DDR3 SODIMM’s (any combination) together it’s usually just fine to mix and match the same types of SODIMM’s together, even if the brand of memory differs. Let’s put this into perspective.

For example, say you have a DDR2 laptop that shipped with a single DDR2 SODIMM. Its capacity is pretty much irrelevant but let’s assumes its 2GB. You now want to upgrade to 4GB but the DDR2 laptop memory upgrade you purchased is of a different brand than the one currently installed (i.e. Samsung Vs Hynix). Will this work? In 99% of cases yes! You see, the brand is for most part a non-issue, what’s relevant however is that both modules are DDR2 thus follow the DDR2 SODIMM specification.

Even if the memory timings differ between the modules then this is also acceptable (unless you want every ounce of performance you can get). The only aspect you should pay attention to when purchasing is the memory speed. For example, if that current 2GB RAM is of the PC2-5300 (667MHz effective) variety, you want to make sure your new DDR2 laptop SODIMM is also at least PC2-5300, otherwise the memory controller within your laptop will be forced to run both SODIMM’s at the speed of the lesser (i.e. slower) SODIMM. To extrapolate this further, PC2-5300 and PC2-6400 DDR SODIMM modules will work together albeit at 667MHz and not 800MHz (effective).

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So why will mixing different brands of laptop SODIMM’s only work in 99% of cases. The short answer is incompatibility. The long answer is as follows, some lesser brands of laptop memory do not always 100% follow the JDEC (the organisation what devises memory specifications) specification, at other times BIOS’s (Basic Input Out System) found in laptops aren’t without bugs. The net result is a laptop that will continuously beep when turned on while displaying a black screen.

Is there a way to upgrade without potentially facing any such problems and diminishing performance? Nothing will 100% guarantee you escape from laptop SODIMM incompatibility issues, after all it’s you who clicks the order button, however as long as you stick to some key recommendations then we’re almost certain you’ll be smiling in no time at all.

Upgrading laptop SODIMM’s – key recommendations to consider prior to buying

We’ve compiled the below shortlist of aspects you should pay attention to when seeking to buy a laptop SODIMM. For peace of mind we recommend that you:

A) Where possible try and buy the same brand of memory to what you already have installed OR buy a laptop memory upgrade from a respected brand

B) Buy the same speed of memory to what’s currently installed, i.e. if PC2-5300 is installed then buy a PC2-5300 laptop SODIMM as it’s very rare that the memory controller in your laptop can run at a higher memory spec, and even if it can, the currently installed slower memory will prevent this (unless you change all SODIMM’s to the new faster spec)

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C) Where financially feasible to do so, always try and buy SODIMM’s of the same capacity to what you currently have installed (see below as to why)

D) If the laptop memory upgrade you plan to buy doesn’t feature a lifetime warranty then it’s best to avoid it altogether, respected memory brands offer lifetime warranties because they believe in their products, so should you (for peace of mind)

E) Simply buy mainstream laptop SODIMM’s rather than performance laptop SODIMM’s. The latter will feature faster memory timings, which offer a modest performance boost. For them to run at these timings however all installed memory modules must meet this spec. As your currently installed laptop will likely feature somewhat slower timings, your laptop’s BIOS will use these, and not the faster timings.

Laptop SODIMM dual channel mode

The vast majority of modern laptops support what is known as dual channel mode. In practise, this means two laptop SODIMM’s are accessed in parallel for enhanced performance (bandwidth).

When dual channel mode was introduced (in DDR memory laptops) it only operated in what’s known as synchronous mode. Newer DDR2 and DDR3 memory laptop support both synchronous and asynchronous mode.

Synchronous mode only works when two identical SODIMM’s are installed. In this case identical also extends to mean two modules of the same capacity, for example, 2x 512MB = 1GB.

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Asynchronous mode on the other hand only works when two non-identical SODIMM’s are installed, non-identical in the sense that they vary in capacity, for example 1x 1GB and 1x2GB = 3GB.

Regardless whether you have an older DDR memory laptop or newer DDR2 or DDR3 laptop, always try and install SODIMM’s of the same capacity. Doing so will ensure your memory (where your laptop supports dual channel mode) runs in synchronous mode.

If you have a DDR2 or newer laptop that supports dual channel mode and install non-identical capacity SODIMM’s, this will force asynchronous mode. In such situation, only part of your memory will operate in dual channel mode, the other part will run in single channel mode.