RAM question

[Chiyawa]

We know that modern consumer CPU has 2 or 4 memory controllers (namely dual channel and quad channel). Each controller can handle 2 sticks of RAM to my knowledge.

 

So, I'm wondering, can a memory controller handle 4 sticks of RAM, or are we hard limited to 2?

 

I've been thinking, since many consumer CPU can support up to 128GB RAM, but however, the maximum memory sticks you can cram to your system are only 4, meaning you have to buy 4 32GB sticks which can be expensive, worst is that if your system already has 4 16GB sticks RAM, you can't use them back.

 

So... What actually define this limitation? I remember back in the old SDRAM days, we can cram 3 sticks of RAM, and I believe there is only one memory controller managing the RAM sticks.

 

Anyway, can anyone explain this to me? I'm just curious about this. I mean, if we have more RAM slots, we can still at least use some of our old RAM back instead to having to replace all of them. 32GB RAM stick is quite expensive.

[Chris Pratt]

It's simply a factor of the memory topology of the board, but the standard is a maximum of 2x the number of channels. Even that is actually suboptimal, as you can often run into issues when using all the slots. Board manufacturers double up the slots because consumers largely demand the ability to "upgrade" the RAM, even though in practice that isn't smart. You're almost universally better off buying a new kit of the capacity you want and just flipping the old kit on the used market.

 

It should really just be equal to the number of channels, i.e. just two for consumer level dual channel systems. In fact, high end extreme overclocking boards do just have two slots, because having four would be counterintuitive to their purpose (you wouldn't be able to OC the RAM as well if you populated all four).

[Chiyawa]

48 minutes ago, Chris Pratt said:

Board manufacturers double up the slots because consumers largely demand the ability to "upgrade" the RAM, even though in practice that isn't smart.

Hmm... Why it is not smart in practise? Well, I mean aside from speed. Is it because of noise?

 

Anyway, this is something I discovered while I'm working with an older system that uses DDR3. I have a bunch of 2GB DDR3, but well, I can only cram a maximum of 8GB into the system. Well, I can get 16GB kit if I want to upgrade it, but somehow, I felt that these low capacities RAM are becoming e-waste, even though they still work fine. Not sure if there's like a RAM switch where you can plop all these low capacity RAM into a big capacity RAM Hmm...

[Chris Pratt]

39 minutes ago, Chiyawa said:

Hmm... Why it is not smart in practise? Well, I mean aside from speed. Is it because of noise?

 

Anyway, this is something I discovered while I'm working with an older system that uses DDR3. I have a bunch of 2GB DDR3, but well, I can only cram a maximum of 8GB into the system. Well, I can get 16GB kit if I want to upgrade it, but somehow, I felt that these low capacities RAM are becoming e-waste, even though they still work fine. Not sure if there's like a RAM switch where you can plop all these low capacity RAM into a big capacity RAM Hmm...

All electronics become e-waste at some point. The goal is making them longer lived, not eternal.

 

It's not smart because it's not trivial to pair different kits of RAM, and it's often difficult, if not impossible, to find the same exact kit years later when you're ready to upgrade. Plus, with replacing it with a whole new kit, you can still maintain just two sticks which is where your optimal stability is going to be. It can also sometimes be problematic to add to your existing RAM. Compatibility issues already mentioned above aside, take my set up for example. I have two sticks of dual rank RAM, giving me four total ranks, the ideal for Ryzen. If I upgraded by adding another of the same kit, I'd be sitting at 8 ranks, which is going to stress the hell out of the IMC, to the point where I might have to downclock my RAM or loosen the timings. That means I'm now losing performance.

[Chiyawa]

30 minutes ago, Chris Pratt said:

If I upgraded by adding another of the same kit, I'd be sitting at 8 ranks, which is going to stress the hell out of the IMC, to the point where I might have to downclock my RAM or loosen the timings. That means I'm now losing performance.

I see. Hmm...

 

Well, thanks for your info. Still, I'm thinking if there's a way to somehow utilised these low capacity RAM, we can at least use it instead of let them sit in the dust or filled up the landfill. Oh well.

 

Here's hoping that probably in the future, either the manufacturer produce a higher capacity RAM of the past generation so people can upgrade their 'old' system. I mean, they don't have to like make a whole batch, just, you know, at least adequate for those who wants to upgrade should the need arises.

 

Ah, too bad. 8GB now just doesn't cut it.

[Chris Pratt]

4 hours ago, Chiyawa said:

I see. Hmm...

 

Well, thanks for your info. Still, I'm thinking if there's a way to somehow utilised these low capacity RAM, we can at least use it instead of let them sit in the dust or filled up the landfill. Oh well.

 

Here's hoping that probably in the future, either the manufacturer produce a higher capacity RAM of the past generation so people can upgrade their 'old' system. I mean, they don't have to like make a whole batch, just, you know, at least adequate for those who wants to upgrade should the need arises.

 

Ah, too bad. 8GB now just doesn't cut it.

We're about to be getting DDR5. Sorry to say it, but if you still have a system with DDR3, it's time to move on. Manufacturers are never going to do anything to further support any components that old.

 

[Chiyawa]

1 hour ago, Chris Pratt said:

Manufacturers are never going to do anything to further support any components that old.

Indeed, but somehow, even when things getting more and more sophisticated, do we really need DDR5 or PCIe 5? Well, guess that's one of the way manufacturer asked you to buy new stuff.

 

Still, guess now I'm going to save up some money and buy a lot of DDR4 16GB RAM. I know someday people might want it. Problem is, where can I get that much money...

[Chiyawa]

Well, this is a workstation and it already has 64GB of RAM. My issue now is that if you want to upgrade the system RAM further, you need to replace those 4 16GB RAM sticks and get 4 32GB RAM sticks which can be very expensive, not to mention that those 16GB RAM sticks are just recently added (about a year ago). You can sell off those 16GB sticks of RAM but the return are a little bit diminishing.