[SOLVED] Pairing a stick with a similar one.

[JRMoore]

Hi, I'm looking to upgrade 2 laptops from 8 to 16 GB of RAM and I could use a bit of advice.

One has an i5 6200U, currently populated by 2 4 GB sticks and the other has an i5 8265U with an 8 GB stick. Since I already have 2 8 GB sticks (8GB 2Rx8 PC4-2400R-SB1-11), so the cheaper route would be to use those sticks in one of the laptops and find a sibling for the one 8 GB one currently in the 8265U machine.

Unfortunately, I think the exact model isn't an off the shelf one so finding an identical stick is not possible. I found most manufacturers don't provide spec sheets as detailed as I'd like, but I think I found a pretty similar one from the same manufacturer.

This would be the details of the one I have:

And the one I think is similar would be another Kingston, a KVR26S19S8/8 (official datasheet) which I can get for 55€ ($62 or £47.50 approx). It's also a 2666 MHz memory with 1 rank and its CL, tRCmin, tRFCmin and tRASmin seem to be the same. Is there anything else I should be taking into account? I found a cheaper 8 GB 2666 MHz CL19 stick from Crucial, a CT8G4SFS8266, for 49€ ($55.30 or £42.30 approx.) but I couldn't find much info about it, so I guess it'd be better to go with the Kingston one right?

Still, I find it odd that the machine came with a 2666 MHz stick, according to Intel's specs for the 8265U it's not among the supported frequencies and XMP is non-existing in that laptop. So at worst the memories would be running at 2400 MHz, but I don't think there's much difference day to day to be honest.

As for the older machine, the one sporting the 6200U the max. supported memory is 2333 MHz, so whatever set of sticks I choose to populate that machine in the end they're going to be running slower than they're capable of; but it's cheaper to use what I have and get a pairing stick for the one that came in the newer machine than to get matching 2333 MHz sticks. Besides, they all should be capable of running at 2133 MHz.

Anyway, for completeness, these are the specs of the matching Crucial sticks I have (2 of the following):

And this is what the 6200U has right now (2 of them):

If you have any advice, for example which set you'd put in which machine, or know of a closer match for the Kingston stick that came with the laptop do let me know. Any input is appreciated, to be honest all of this is pretty much outside of my knowledge area.

Thanks anyway for your time!

P.S. Is there a way of knowing the actual clock speed the RAM is working at? For example, in the task manager the 8265U machine shows RAM being 2400 MHz instead of 2666, so there's no way it's running at 2666 MHz. right?

 

[TechyInAZ]

It is a risk no matter how you look at it. Even if you get a stick of memory with the exact same primary timings, there is still a chance of it not working (because that stick might require different subtimings). Now, Intel's memory controller is pretty good when it comes to weird memory configurations, but I cannot guarantee anything. The only way you can guarantee the sticks will work is if you buy completely new dual channel kits and replace all the memory.

As for seeing what your memory frequency is, task manager is good. But if you don't trust Task Manager, run CPU-Z and go to the memory tab (CPU-Z sees the memory speed in half because of how DDR (double data rate) memory works, so take that memory speed x2 and that'll be your actual frequency.)

 

[Calvin7]

Memory is guaranteed in the form sold. Use of identical, exact match, same thing may give you a better chance of working together over the use of random modules, but have no guarantee to be compatible together.

Combining multiple modules sold as Singles may cause the memory to be no longer able to operate at rated specifications. You might get it working by running at a slower clock speed.

 

[JRMoore]

Thank you for the replies TechyInAZ & Calvin7!

From the looks of it there's no certainty even when pairing 2 sticks of the same series and model that are sold individually, I thought adding more RAM to a machine was an easy upgrade. Curiosity makes me want to give that Kingston a try, but I don't think it's worth it and at this point in time I'm not in a position to make gambles.

So for the 8265U machine I'm going to use the set I already have, and for the other machine I found a 2133 MHz G.Skill set (F4-2133C15D-16GRS) for 95€ ($107.25, £82); so I'll get that instead and then sell the leftover sticks if everything works as expected.

By the way, I couldn't find anything conclusive whether the current RAM on that 8265U is running at 2666 MHz or not. Everything seems to point out it's running at 2400 MHz though which would match the processor specs.

The memory tab in CPU-Z only showed the total amount of system memory (the rest was empty for some reason), but the SPD one identified the RAM type correctly. I tried other programs like HWiNFO and my guess is that the 2666 figures that appeared in some were only because they were identifying the stick, not the clock speed in use.

It's of no consequence, I don't think it'd make that much of a difference, it was more of a burning question given that they chose to put a 2666 MHz stick in the machine.

 

[TechyInAZ]

As you said 2400mhz is the max officially supported memory speed by Intel's CPUs. I think the reason why they put 2666mhz is because it is cheaper, 2666mhz is really cheap to make as almost all DDR4 chips can hit that frequency. So it could be that in the current state of the market, 2666 is cheaper than 2400 which I have seen before.

If you go into the BIOS, you might be able to run it at 2666mhz. But I highly doubt it. Then there are some laptops who have smart enough BIOS's that automatically run whatever memory it has at it's rated speed which is super sweet.