Which RAM do I need?
The questions we are asked most, answered properly. If yours is not here, ask us — we would rather answer first than take a return later.
Will DDR4 fit in a DDR3 slot?
No. The notch in the bottom edge of the module is in a different place for each generation, so a DDR4 module will not physically seat in a DDR3 slot, and forcing it damages the slot. DDR5 is different again. Check the label on the module already in your machine: it will say DDR3, DDR3L, DDR4 or DDR5.
What is the difference between SODIMM and DIMM?
SODIMM is the short module used in laptops, mini PCs, all-in-ones and many small-form-factor desktops. A full-size DIMM is roughly twice as long and goes in a standard desktop or server board. They are not interchangeable in either direction.
What does 1Rx8 or 2Rx8 mean, and does it matter?
It is the rank of the module: how many independent sets of chips it presents to the memory controller. 1R is single-rank, 2R is dual-rank. Most machines take either, but some laptops and many servers are specific about it, and a few will not boot with the wrong one. If your motherboard or laptop manual specifies a rank, match it. We list the rank on every module.
Can I mix memory of different speeds?
Yes. All the modules fitted run at the speed of the slowest one, and at whatever the machine itself supports. So a 3200MHz module in a laptop that supports 2666MHz simply runs at 2666 — it is not wasted, and it is not a problem. Mixing capacities is also fine, though on some machines it disables dual-channel mode and costs a little performance.
Can I use ECC server memory in a normal desktop?
Almost never. Registered ECC memory (RDIMM) needs a board and processor that support it, which in practice means a server or workstation platform. An ordinary consumer desktop will not post with an RDIMM fitted. Your motherboard manual states clearly whether registered memory is supported.
What is the difference between DDR3 and DDR3L?
DDR3L runs at 1.35V, standard DDR3 at 1.5V. A DDR3L module works in almost any DDR3 machine, but a 1.5V DDR3 module will not reliably run in a machine that expects DDR3L only — which includes a lot of laptops from about 2013 onwards. Where a module is DDR3L we say so.
How much memory can my laptop take?
Two things decide it: how many slots the machine has, and the maximum each slot accepts. Many thin laptops have memory soldered to the board with one free slot; some have none. The quickest check is to search your exact model number plus "memory upgrade" or to open the panel and look. If you tell us the model we will tell you what fits.
Is used memory reliable?
Memory has no moving parts and no meaningful wear mechanism, which is why used modules are a sensible buy in a way that used drives are not. A module that passes a full test is very unlikely to develop a fault later. Everything here is tested in a working machine at its rated speed before it is listed, and again before it is packed.