Okay, I've been wanting to upgrade the RAM in my desktop forever and I've decided that I'd better while I can still afford to. This is an older but very capable machine running Win7 64-bit. It currently has 1600MHz DDR3 DIMMs installed. Two Corsair brand ones and they say on the side, 8GB (2x4GB). I'm thinking I should get two more that are identical to these, since if I'm gonna use all four RAM slots, the MoBo manufacturer requires that all four be identical.

But here's where I'm getting confused. As mentioned above, I have two of these modules in my machine right now. And when I do the Windows System Properties page, it shows 8 GB. But when I look at some of the listings for these DIMMs on eBay, they're indicating that two of these modules are good for 16 GB. I guess it makes sense, since each module sez 8 GB, but I guess what's throwing me is the (2x4GB) that also shows on the sticker. And these ones they're saying are good for 16GB are absolutely identical to mine, even with the same long part number, i.e., CMX8GX3M2A1600C9.

So, if two of these DIMMs really amount to 16GB, then I've been running my system on a single DIMM all these years with the other one being no good. But that doesn't seem likely. I've had other motherboards where a bad ram stick was installed and the board would indicate a memory error on boot-up. But even more to the point, I don't recall buying 16 GB of RAM and I'm thinking that I would have noticed this deficiency like right away.

So I guess it's a terminology thing? And if that's the case, then why does each DIMM's sticker say 8GB, when it is actually only 4GB? Are they meant to be used in pairs only? I'm so confused.

Corsair sells RAM 'kits', which are intended to be installed as a pair.

Couple examples of 8GB kits that are actually 2X4GB below. One from Amazon and one from Corsair <grin>.

Maybe your kit was labeled as such since they were meant to be installed as a matching pair (or kit).

RAM can be a funny thing; it's possible to have mismatched sticks (say a 2gb & 4 gb) and show 6GB in the OS .. but the speed of one may affect the performance of the other. So a matching pair is desirable, and it looks like they may market to that aspect.

https://www.amazon.com/Corsair-CMX8GX3M2A1600C9-1600MHz-DDR3-DIMM/dp/B004U7T7NA
https://www.corsair.com/us/en/Categories/Products/Memory/High-Performance-Memory/Vengeance%C2%AE-%E2%80%94-8GB-Dual-Channel-DDR3-Memory-Kit/p/CMZ8GX3M2A1600C9

Crucial is a memory chip manufacturer. Their site is a good starting point for thinking about memory expansion. +++ This Link +++ will provide the background information and +++ THIS +++ link will scan your computer and advise you about exactly what memory you need.

OK, guys, thanks for the info. It was very helpful. Rharv, yes, you're right -- my Corsair memory sticks are obviously meant to be installed as a pair. A big reason why I was thinking about getting another identical pair, which would push my system memory up to 16GB, which is where I think it needs to be. My motherboard, an ASRock 890GX Pro3, will handle up to 32GB. I would like to go ahead and install the max, but I've got the necessary funds to do this earmarked for other things.

Jim, thanks for the links. Your second link leads to a screen where Crucial shows their selections with prices. Surprisingly, their prices are some of the cheapest I've seen, especially for new RAM. I visited Corsair's website, and their prices are significantly higher, although the eBay sellers of Corsair RAM have their prices adjusted more toward real street prices.

As a follow-up to this, one of the problems I'm having with my system (Win7 64 bit, although lately I've been running BiaB 32 bit) is pops and crackles and hesitations. I have to have just about everything else put away, and I'll even call up Windows Task Manager and stop several applications which load themselves on system start up. I have to do this to ensure a clean sounding playback in both BiaB and Cakewalk by Bandlab (formerly Sonar Platinum). I'm hoping that by doubling the system RAM I won't have to be quite so rigid in trimming things down so the music stuff will run right. One reason for this is that, now that I have a digital mixer (Behringer XR12), I also now have a big mixer screen that must be present to operate the mixer -- while either BiaB or Cakewalk are running. Fact is, I'd like to be able to have both BiaB and Cakewalk up at the same time, but I usually can't do this. I'm hoping 16GB will be enough extra memory so I can make it happen.

Just to be clear, when you see 2x4 or 2x8 (or even 4x4), it means you are getting two RAM sticks of however many gigabytes for a total of what is being sold. Oftentimes you also see 1x8 (which means a single 8GB RAM stick). If you purchased two 1x8 of the same brand, it's the same as buying the 16GB 2x8 package.

So 8GB RAM designated as 2x4, means you are getting two 4-GB RAM sticks. 16GB RAM designated as 4x4 means four 4-GB RAM sticks and 2x8 means two 8-GB RAM sticks.

First thing to do is make sure how much RAM your motherboard will hold. My laptop, for example, will only allow 8GB RAM and currently has 2 4GB RAM sticks installed (my bad for not checking this when I bought two 8GB RAM sticks to try to get it to 16GB, but I bought that when RAM was really cheap, so I was only out about $50, still...should have checked). The Crucial site mentioned above is an excellent resource for replacing RAM. You don't have to ultimately buy from them, but you'll ultimately know what to buy.

cooltouch reading your initial post you seem to be wondering if your computer is seeing both DIMM's and reporting both of them as a total of memory available, correct.

You can usually do this quite easily from the BIOS of your computer. It may not be obvious what to look for there. However there are free tools that will give you that information if you are not comfy delving into your BIOS.

A good one is 'Speccy' by Piriform, it will tell what slot numbers are populated on your motherboard and what size DIMMs are fitted.

Simply download, install then run the app and you will be presented with a summary of various aspects of your machine. click on the 'RAM' section and the main screen shows more detail of the RAM you have starting with how many slots are populated and how many are free, then various data about the speed of the fitted RAM, at the bottom you will see 'SPD' (Serial Presence Detect) which will show you which DIMMs are functioning, it shoud be two in your case.

If it shows only one then one of yours is either defective or not fitted properly. If it does show 2 then you've just confirmed you have two correctly functioning 4Gb DIMMs. You can then click on the 'Slot #n' titles being shown and see more detail about your physical memory.

Speccy is available here.

https://www.ccleaner.com/speccy/download/standard

If you do want to add more ram then the earlier link to the 'Crucial' scan tool is a good idea as it will tell you exactly what options you have to upgrade.

So now you have the 'skinny' too!

btw the SKU number you provided CMX8GX3M2A1600C9 does indeed point to an 8Gb (2x4Gb DIMM) kit, on the Corsair web page.

https://www.corsair.com/uk/en/Categories/Products/Memory/XMS3-%E2%80%94-8GB-%282x4GB%29-DDR3-1600MHz-C9-Memory-Kit/p/CMX8GX3M2A1600C9

Thanks for everything, guys. As I mentioned above, my motherboard will handle up to 32GB, but I'm just gonna take it up to 16GB for now. I hope that will be sufficient. This motherboard employs Dual Channel Memory technology, where each pair of RAM slots is one channel. It also states that all four DIMMs must be identical, down to the manufacturer of the chips. So I'm stuck with having to add a pair of Corsairs to the system. Not so bad, I suppose. At least they're still available.

Jonbouy, I don't really need the app. I have my machine sitting right next to me with the sides off. All I gotta do is lean over to inspect the RAM slots, two of which are still open. I built this machine, so I kinda know it inside and out.

Sorry I thought you were the poster that asked this.