3 DIMM slots in 2010 MP, 4th slot empty. Can I add another stick?

Yes you can add moar ramz

Hello,

Older 8GB ram sticks had to match. Try getting another identical RAM stick, from the same company. If you bought it from OWC, ask them before buying.

Loa

P.S. You probably used only 3 slots because someone told you that it would make your RAM faster. To make along story short: it was a lie!

You should check your actual memory usage statistics before buying another DIMM. You may not benefit from 32GB over 24GB.

Get the part number of a module and post it here. 8GB DIMMs were only available as Registered ECC 2 years ago, but much is Unbuffered now. You can't mix them.

If you bought a matched set of 3x8Gb ECC a few years ago and now want to go to the full 32Gb, providing you match the RAM speed, timings and ECC but use a different manufacturer, you *should* be OK.

If the timings are different but everything else is the same, the worse case scenario is that you have to replace one 8Gb and buy a matched pair.

Remember ECC and non-ECC do not mix.

Why don't you post a pic of one of the sticks showing the sticker with the part number (make sure it is in focus). Someone might be able to suggest an exact stock number at an e-shop for the fourth stick. Just say which country you are in so they don't recommend a shop on the other side of the world.

Failing that, tell us what it says on Apple - About this Mac - More Info - Overview. You are looking for a line that says something like...

Memory 24 GB 1333 MHz DDR3 ECC

The key here is to see if you are using ECC or non-ECC memory. That is all you have to match if you want to take out the third stick and replace it with a new, warrantied matched pair.

On the assumption that you currently have a matched triple of 8Gb ECC sticks, you would be able to take one out and replace it with a matched pair of anyone else's 8Gb ECC sticks.

As long as all four sticks are EITHER ECC OR non-ECC you will be fine regardless of the brand. Just check the warranties and don't necessarily go for the cheapest option.

malch said:

Thank you all! Some really interesting information, that I never would have found on my own. Much appreciated.
Loa—you are absolutely right. I do remember hearing that 3 sticks would be better, for technical reasons that were beyond me... and I ended up getting 3 for that reason.
Umbongo and Daniel—I'm nervous about getting a wrong (unmatching) stick of 8GB, and ending up with four slots full but just three working. If I splurge (it's Christmas, after all) and get two new sticks of 16GB, will this work?
Or will it matter that these two new sticks might not 'match' my other two sticks of 8GB?
Umbongo—I'm a video editor, using Avid Media Composer. I've always assumed that more RAM is better, but maybe I should check into this, specifically for Avid.
Thanks,
malch

Click to expand...

Technically 3 sticks will be faster to access than 4 but the difference is so small that you are only going to see it on benchmarks. This is because it uses a tri-channel I believe.

The reason for Umbongo's comment is that RAM is only useful if you are using it. If during your daily use of your computer you never utilize all your RAM then adding more wont make a difference. If you find yourself running out of memory and swapping to disk then you need more RAM.

That said, empty slots make me angry so I would fill it. You know, just to keep the dust out.

Would your memory be quad rank? Might be worth considering - not sure of the performance hit in real world but it will down clock if it is quad rank.

You won't get any popups or warnings that you're out of memory.

To see if you're using swap:
1) Open 'Activity Monitor'
2) click on the 'System Memory' tab.
3) look at 'Swap used'

That's the amount of swap space you have used since the system booted.

If it says '0 MB', then you won't benefit from adding more ram.

malch said:

Umbongo—I'm a video editor, using Avid Media Composer. I've always assumed that more RAM is better, but maybe I should check into this, specifically for Avid.
Thanks,
malch

Click to expand...

More RAM is only useful for Avid MC 6 and up. It's useless for any version before that as it was 32 bit until v6.

malch said:

I also found my bill from OWC, which describes my order like this:

Quantity: 1 OWC1333D3X8M16K, $667.99 each
16GB (2x8GB) DDR3 ECC PC10600 1333MHz SDRAM PC3-10600 ECC for Mac Pro 'Nehalem' & 'Westmere' models. Lifetime advance replacement warranty

Click to expand...

So what have you actually got in the third slot then? That invoice was just for a pair of 8Gb. Do you actually have two slots free or what?