Fast and slow RAM in single machine

Question

I'm thinking of building a new machine for my work, gaming and tinkering with VMs and I'm a little on budget. To keep the work part fast I want as fast RAM as possible, but they tend to be expensive. So I thought about having let's say 8GB of very fast and expensive RAM and then maybe 64GB of cheaper and slower ones.

Is there a way to make this work (on Linux, preferably)? Another problem is that motherboards in my price range don't support that much ram directly (and also 4GB sticks are the cheapest, so that would require even more slots.

What I was thinking about was getting a PCIe ram disk thingie, put the cheap ram into that and use it as swap with swappiness set to maximum. Is this feasible?

Answer 1

What I was thinking about was getting a PCIe ram disk thingie, put the cheap ram into that and use it as swap with swappiness set to maximum. Is this feasible?

Those things are expensive, and don't give you much bang for your buck. Your VMs typically won't use swap that way, and you're better off adding swap in the VMs as needed.There's fast (or fairly fast) sata or NVMe drives that would work well though, and will give you better speed and capacity than those ram drives at significantly lower cost. For that matter a new motherboard and processor may be a lot cheaper than a PCIe ram disk. Most of the ones I've looked at are "contact us for prices"

So I thought about having let's say 8GB of very fast and expensive RAM and then maybe 64GB of cheaper and slower ones.

This is... kind of a bad idea. Ram will always run at the speed of your slowest ram. And in most situations, high frequency ram gives you a minimal advantage. Go with price and quantity over speed.

Another problem is that motherboards in my price range don't support that much ram directly (and also 4GB sticks are the cheapest, so that would require even more slots.

Go with 2x8 to start with. They arn't that pricy and you can go 2x16 on DDR4 in future, or such. I've actually gone with 8gb on my dedi and I don't really feel the pinch.

Answer 2

It depends on the usage you want to do with it, but the main issue is do you need a lot of RAM for multiple softwares, or do you have a single soft (aka a memory intensive algorithm or a 3D Engine IDE) that will benefit from faster RAM.

Usually, faster RAM doesn't give a huge boost (around 10% on some AAA games) in classic applications (games, everyday productivity, etc..) yet having fast RAM is futureproof, and is always welcome.

If you are going to run several VM's and a lot of programs at the same time, fast RAM won't save you from swapping on disk, and will be the bottleneck of your machine.

You should aim for the sweet-spot of decent amount of RAM (depending on your needs, 16GB are now correct for a power user nowadays) and the fastest frequencies and best timing you can get with that budget.