Looking to upgrade the RAM on a relative’s computer. I have a couple questions.

There’s a bit to unpack here. To start, are we talking about a laptop or a desktop? Any more detail you can provide?

You can use different speeds together, but they will function at the lower rated DIMM's speeds

Would be easier to just upgrade to two 8gb DIMMs or a single 16gb DIMM

It’s a desktop. I was doing a bit of reading before anyone replied to this thread.

From what I’ve gathered, I’d want to use 2400 since I don’t know if the motherboard can handle 3200. Seems I’d just remove the 4g and replace with two 8g.

If you care to read the specs, here’s they are for his specific desktop. He has the core i3 processor:

https://psref.lenovo.com/syspool/Sys/PDF/IdeaCentre/ideacentre_510S_08IKL/ideacentre_510S_08IKL_Spec.pdf

It looks like the CPU is spec'd for 2400 but there is a line that says "or 2666". I don't think you'll get much out of the 2666 over the 2400. Its dual channel compatible, so you'll want to get 2 x 8GB DDR4-2400. Not 1 x 16. It isn't compatible with that.

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It looks like the CPU is spec'd for 2400 but there is a line that says "or 2666". I don't think you'll get much out of the 2666 over the 2400. It’s dual channel compatible, so you'll want to get 2 x 8GB DDR4-2400. Not 1 x 16. It isn't compatible with that.

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That’s what I was thinking. Thanks for the confirmation.

1x16gb would work fine.

Often times you can buy faster RAM than motherboard spec, it'll just run at the motherboard max spec

With the manufactured PCs, you have to avoid the gaming RAM which is typically cheaper. You have to get the full on jedec rated memory sticks. You can get something that is rated faster but make absolutely sure it has JEDEC timings for the rated speed of that PC.

I made the mistake of buying non-JEDEC RAM for an HP and it wouldn't work at all. Lots of learning that night since it had been 20 years since I built a PC. So much has changed.

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With the manufactured PCs, you have to avoid the gaming RAM which is typically cheaper. You have to get the full on jedec rated memory sticks.

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Rephrase?

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Hard to rephrase it much more but I will try.

Gaming RAM: Typically this will reference XMP or XMP2.0. This memory standard allows varying speed and voltages. These features are typically limited to 3rd party motherboards you can buy yourself. Maybe if you buy a "gaming PC" it might come with a motherboard chipset that supports XMP.

JEDEC RAM: JEDEC is the typical standard for RAM timings but it doesnt allow for things like overclocking, voltage changes, etc, that gamers typically go after. If the RAM being looked at does not specifically list JEDEC timings and speeds, it is probably not going to work in a HP, Dell, etc.

TLDR example - an XMP gaming RAM stick saying it will work at 3200MHz will 99% likely NOT work in a standard HP, Dell, Lenovo, etc. motherboard requiring JEDEC RAM. If the XMP ram works, it will probably operate at a MUCH lower speed. If the RAM doesn't specifically list JEDEC 3200MHz, it isn't going to work because it will have a more demanding voltage requirement and gaming RAM wont cut at those voltage levels.

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Ok, I think I see where our disconnect is.

While I'm by no means a RAM expert, my understanding is that all RAM and all motherboards have a basic JEDEC profile. As an example, the kit I'm running is rated out of the box at XMP 3600mhz at CAS 14 at 1.45v (which I have OC'd to 3800mhz at 1.5v, but that's neither here nor there), but when you first install and boot up that kit, it boots at the base JEDEC spec, which I believe was 2666mhz at 1.2v. Now, would it be a massive waste of money to run it at JEDEC? Of course. But I'm fairly certain it will "work" in any DDR4 compatible board, simply at that lower speed and voltage.

Now, with that said, you are absolutely right that if you plug a kit of JEDEC 2666mhz XMP 3200mhz RAM into a board that doesn't support XMP, you're only going to get the 2666mhz. So, if you want the 3200mhz, you need to buy a kit that has a base JEDEC profile of 3200mhz.

Finally, while I might be inclined to dicker over whether lower or higher voltage tolerances are "more demanding", that's getting far beyond the scope of this thread, so I'll leave that for another day

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I'm not sure all RAM does. When I purchased some memory a couple years ago for an HP, the system wouldn't even boot let alone boot at a lower memory speed. The RAM simply wouldn't run at 1.2V. It needed a higher voltage which the MB just couldn't provide so it errored out at boot screen.

I tried Crucial Ballistix 3200Mhz ram. It said it "could" run at a JEDEC default profile but the issue was even at that it required a voltage of 1.35V. So it failed.

I then went with basic Crucial RAM that adhered to JEDEC standards of 3200Mhz at 1.2V and worked perfectly. Many times people want to avoid the standard memory due to the slower timings but getting ram to operate at lower timings and 1.2V is very difficult.

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That's... odd. Did you try multiple kits, or just that one Ballistix kit? I ask because after a quick google, it seems like a common issue for people to run into that JEDEC isn't loading properly on that particular kit, for whatever reason. If you tried multiple kits, again, very odd.

As an example, take this very basic single stick of RAM with an XMP profile: LINK

If you scroll down a touch and then click the "Tech Specs" tab, you'll see that the XMP profile is rated for 3200mhz CAS 16 at 1.35v, but it also lists the base JEDEC profile (labeled SPD) at 2133mhz CAS 15 at 1.2v. I've only installed a handful of RAM kits, but l've literally never had one not initially boot with its base 1.2v JEDEC specs (ignoring bad kits of RAM that don't boot at all, which is a separate issue).