RAM Compatibility – Risks of Purchasing Two Kits of 64GB RAM Instead of One 128GB Kit

compatibilitymemory

Manufacturers of RAM, specially gaming RAM, sell 64GB kits of RAM (4 x 16GB modules), and also 128GB Kits (8 x 16GB modules). In one of the reviews of 64GB G.Skills Ripjaws V kit, one customer says that:

G.Skill and most memory makers do not guarantee two kits of RAM to work together. So if you are hoping to use two of these kits on a MB that supports 8 x 16GB RAM, you would be better off buying a single 8 x 16GB kit instead.

What is the meaning of not giving a guarantee that two 64GB kits will work together? I am asking since two 64GB kits like the ones mentioned would cost $510, whereas a single kit like this would cost much more, more than $600.

My question is, is it risky, might not work most of the time or sometimes, or causes problems only when overclocked? If anyone with experience can answer it would be helpful. I am assuming the motherboard can CPU can take 128GB RAM.

My own experience and search says the setup of two kits should work, since I have seen modules purchased at different times work together (one original, and second as update later, same manufacturer but different series). If speeds are different, system adjusts to the lower speed. If the configuration is not optimal, like 2 modules in slot 1A and 2A instead of slot 1A and 1B in dual channel gives warning on boot but otherwise works fine. Also kits are matched to give best performance but separately purchased modules of RAM should work fine, maybe a little slower, according to my understanding.

So is it a high risk purchase, low risk purchase or best avoided and my understanding is incorrect?

Best Answer

What is a matched set?

Matched sets are guaranteed to work together at advertised speed, assuming no motherboard incompatibilities or defects. 2 sets of same speed, same brand and same model number are not guaranteed to work well together. It's better if they come from the same production batch, but that still does not equate a matched set, as from what I understand a matched set has been tested (to a degree) during the binning process.

Number of sticks

In addition to the risk of unmatched set, I believe that using many sticks increase the likeliness of encountering the "limits" of the motherboard and trigger incompatibilities with the RAM. Unfortunately I don't have evidence to back this up, but I have had the experience of sticks that all tested fine independently, but failed as a cluster.

If your question was about 2 sticks I'd probably tell you to go ahead and try it, with 8 sticks I'm much more cautious.

RMA considerations

If you run into issue, the RMA process will be much simpler with a matched set. I've had some issues with a new 6 stick matched set a few years back, and had to RMA it 3 times before getting a good one. It would have been troublesome to have 2 independently working products on hand, but failing as a set. Which one is causing problems? What is the chance of exchanging both to fix the issue?

However, you can do solve all those issues that at no cost to you during the return window, and save some money. Whatever you order, make sure to configure them to run at advertised speed, and memtest this seriously. If they work well from the get go, chances are you will be fine for their lifetime.

If a stick later fail under warranty you can RMA that particular set only and pray you get a compatible set in return. But that's only a chance, and much more in the future - so it depends how much you value those savings today.

Underclocking and testing considerations

I think you alluded running them at a slower speed than advertised if you run into issues. That may ease the load and avoid incompatibilities, but figuring out the working configuration is like overclocking - you'll have to do a whole lot of testing to find what frequencies and timings do actually work, if any, and testing 128GB each time is going to take a while. If you settle for frequency and timing that are much lower than needed, you have to consider that the money saved is being eaten away a little by the lower grade of RAM speed you are benefitting from.

TL;DR

For that many sticks and amount of RAM, my personal recommendation would be a matched set. But it's certainly not a bad decision to try it out if you're willing to risk having to go through a return process early on -- and maybe only switch to a matched set if issues do arise.

Related Solutions

Windows – Determine RAM clock timing in Windows 10

This can be easily done within PowerShell using the following commands:

Get-WmiObject win32_physicalmemory | Format-Table Manufacturer,Configuredclockspeed,Devicelocator,Capacity,Serialnumber -autosize

This will give the following as output:

You can also get this through Command line using the following command:

wmic memorychip get Capacity, MemoryType, Speed, DeviceLocator

..which would give the following output:

Should I buy 16GB ram as additional slot for the 8GB ram laptop? or an 8GB

In general, it depends on a few things.

The biggest question is going to be, Is the new ram going to be compatible with the old ram and is the new ram compatible with the motherboard?
Does the motherboard has dual channel memory support, or something alike? If so, 2x 8GB will outperform 1x16GB.
Is the price for 1x16GB justifiable compared to 1x8GB, considering that the 1x8GB works and won't give any advantage to 1x16GB?
Do you have considerations to upgrade the memory in the future again and does the maximum memory supported by the laptop has 2x16GB (32GB) support?

If you answer these questions, you have an answer for your question. I'm not going to write it differently, because that would turn this into a hardware recommendation answer, and that is considered Off-topic. My goal here is to teach you how to get the information you need to make the decision yourself, so that others who find this answer can do the same.

Here are a few comments based on the 4 answers given above: 1. Both ram should have the same clockspeed, type and latency settings. If this is not the same, the system may be unstable or give BSoD's frequently. Preferably, the RAM should be from the same manufacturer, and if possible if they are identical, that would give the best results.

If the motherboard has this feature, it will read and write data to both memory sticks at the same time boosting performance. For this to work, the memory sticks should be identical.
If the price for 1x16GB is less than twice 8GB, it could be benefitial to go for the 1x16GB. Likewise, if the 1x16GB is quite a bit more expensive twice 8GB, even if you can't get dual channel working, getting 1x 8GB may be worth it more.
You need to look at how old your laptop is. Do you think you will be upgrading your laptop again with memory in the future, or is it likely that at some point the laptop dies or you otherwise replace it, if you don't plan on upgrading in the future, getting 1x16gb is only a good idea if you get a crazy deal pricewise. Otherwise, consider 2x 8GB, if you are unsure the memory is going to be compatible.