How to find the appropriate RAM to upgrade?

Question

I want to understand how to upgrade RAM on a computer, and everywhere I see something else to consider to upgrade.

What is the full formula or algorithm?

What decisions are derived from the mother board? What decisions from other memories?

Answer 1

There are many resources on the web for this sort of question. Start by reading on Wikipedia and vendor sites about DDR3, DDR4, ECC, XMP. Watch Youtube for demonstration of grounding yourself and installing. Don't worry about CAS timings until you have upgraded or built a PC successfully.

Note : The motherboard dictates what kind of RAM you get. Not all motherboards support all RAM. Make sure that you buy from a retailer with a return policy.

Motherboard support

If the PC is from a builder like Dell or HP, start by looking up the model. Usually the RAM type is listed like DDR3 1600 MHz or DDR4 2400 MHz. It may be listed as PDC3-10600 or PC4-### , which is another numbering scheme.

If the PC is custom-built, then start by looking up the motherboard supported RAM speed from the motherboard manufacturer.

DIMM or SO-DIMM

There are two common RAM sizes - DIMMs for desktops, and smaller SO-DIMMs for laptops.

ECC

Most motherboards don't support ECC. Some require ECC. Some allow it without requiring it - confirm with the documentation. If the documentation doesn't mention ECC, don't buy ECC RAM.

Kit

Always purchase RAM in kits (pairs or quads). Don't mix and match them from different kits. The system will run at the slowest one installed, and you may find weird problems resulting from timing differences.

Rate

Motherboards will default to running RAM at a standard rate (1600 MHz for DDR3, 2400 MHz for DDR4). This is fine in most circumstances. If you're not building a very fast AMD PC, then higher-rate RAM does not help much.

XMP

Once you confirm that it's working at the slower rate, you have the option to turn on XMP (eXtended Memory Profile) and attempt to run the RAM at a higher rate. This is hotter and uses more electricity, but should work as long as both motherboard and RAM are rated for it.