Best performance setup for installing RAM?

[BenBRockN]

I have a question... Maybe the LMG team can do some benchmarks on it.

 

(A) If you have Dual Channel (4 slots, assuming slots 1&3=1, slots 2&4=2) on your Mobo of 16GB of RAM, what is the best configuration?

 

(1) 1x16 GB single channel

(2) 2x8 GB single channel (slots 1&3)

(3) 2x8 GB dual channel (slots 1&2)

(4) 4x4 GB (all slots)

 

(B) Does Intel Quad Channel boards (assuming 4 slots) make any difference, or is there a sweet spot for that configuration too?

 

Thanks,

- Ben

[App4that]

2 or 4, no difference between them other than the smaller dimms tend to OC better. 

[Enderman]

It doesn't really matter.

If you want it to look good get 4x4, if you want to upgrade in the future then get 2x8.

There is no point in worrying about some speeds that you won't even notice int he real world.

[BenBRockN]

In the past, with previous versions of DDR RAM, didn't the placement matter for performance? Technically it should still matter since the more RAM you use (slots), the more voltage your mobo needs & the more the memory controller has to switch to the correct RAM in those slots (more work),  which makes it less efficient than using less RAM slots. But if you only use one stick of RAM (16GB), then you aren't utilizing the dual channel capability, so there should be a loss in performance. I'd rather have some benchmarks on this to be honest, but I haven't seen this tested anywhere.

[porina]

For Prime95 large FFT and similar workloads:

 

Joint best: 4x4 GB single rank, or 2x8 GB dual rank modules, running dual channel. On most mobos with 4 ram slots, positions 2 and 4 are recommended.

Intermediate: 2x8 GB single rank, dual channel.

Big bag of NOPE: 1x16 GB or 2x8 GB on single channel. You're just throwing away bandwidth and performance here...

 

In my testing dual rank per channel of the same speed and timings gives up to 20% performance boost in memory intensive bandwidth limited work compared to single rank per channel. It doesn't seem to matter if dual rank modules are used, or two single rank.

 

In synthetic benchmarks like Aida64, dual rank over single gives a slight increase in bandwidth, but also a slight increase in latency. Certainly not of the magnitude in the improvement observed. Also latency seems to have a much smaller influence than rawr speed so given the choice, I'd prioritise a dual channel dual rank kit as fast as reasonably possible (don't over-pay for it), with latency down the list. For DDR4, 4GB modules are single rank. 8 GB can go either way, with faster and/or tighter timing kits tending towards single.

 

Similar applies to quad channel ram, but you have to consider the ram speed proportionate to the total CPU demand it is supplying. More cores at more clock means you should ideally consider faster ram to keep up with it.

 

I go into this in a bit more detail in following thread:

 

 

[BenBRockN]

[deleted]

[BenBRockN]

1 hour ago, porina said:

For Prime95 large FFT and similar workloads:

 

Joint best: 4x4 GB single rank, or 2x8 GB dual rank modules, running dual channel. On most mobos with 4 ram slots, positions 2 and 4 are recommended.

Intermediate: 2x8 GB single rank, dual channel.

Big bag of NOPE: 1x16 GB or 2x8 GB on single channel. You're just throwing away bandwidth and performance here...

 

In my testing dual rank per channel of the same speed and timings gives up to 20% performance boost in memory intensive bandwidth limited work compared to single rank per channel. It doesn't seem to matter if dual rank modules are used, or two single rank.

 

In synthetic benchmarks like Aida64, dual rank over single gives a slight increase in bandwidth, but also a slight increase in latency. Certainly not of the magnitude in the improvement observed. Also latency seems to have a much smaller influence than rawr speed so given the choice, I'd prioritise a dual channel dual rank kit as fast as reasonably possible (don't over-pay for it), with latency down the list. For DDR4, 4GB modules are single rank. 8 GB can go either way, with faster and/or tighter timing kits tending towards single.

 

Similar applies to quad channel ram, but you have to consider the ram speed proportionate to the total CPU demand it is supplying. More cores at more clock means you should ideally consider faster ram to keep up with it.

 

I go into this in a bit more detail in following thread:

 

 

Wow, so this was the answer I was looking for. When it comes to rank, I've searched Amazon and NewEgg for things such as "2Rx8" or "dual rank", but all I find are a few off-brand sticks that report that. For instance, Corsair Vengence and Kingston HyperX do not report rank either in product descriptions or on the sticker, which I thought was odd because if rank was worth mentioning, the big name companies should be doing it right?. Do manufacturers default to a certain rank (single or dual) for their products?

[porina]

13 minutes ago, BenBRockN said:

Wow, so this was the answer I was looking for. When it comes to rank, I've searched Amazon and NewEgg for things such as "2Rx8" or "dual rank", but all I find are a few off-brand sticks that report that. For instance, Corsair Vengence and Kingston HyperX do not report rank either in product descriptions or on the sticker, which I thought was odd because if rank was worth mentioning, the big name companies should be doing it right?. Do manufacturers default to a certain rank (single or dual) for their products?

For most people it doesn't make enough of a difference to care about. I need to repeat, my testing is only for Prime95 large FFT or similar workloads. This is not something most people care about. It also doesn't necessarily reflect in gaming performance. In some other application, latency might be more important after all, and you either need to test yourself, or find someone else who has done it.

 

I'm also frustrated by the lack of information. If you have the Kingston part number, you can look up its specification, which I've had to do myself. I found their 2666 2x8 GB dual rank kit to be good value at the time I bought it, and this also avoids potential compatibility problems if you go to 3000+ rated kits.

 

Again, for DDR4, you can assume 4 GB modules will be single rank. 8 GB could go either way.

[BenBRockN]

48 minutes ago, porina said:

I'm also frustrated by the lack of information. If you have the Kingston part number, you can look up its specification, which I've had to do myself. I found their 2666 2x8 GB dual rank kit to be good value at the time I bought it, and this also avoids potential compatibility problems if you go to 3000+ rated kits.

 

Again, for DDR4, you can assume 4 GB modules will be single rank. 8 GB could go either way.

I heard that mixing ranks (accidentally installing single & dual rank RAM) would significantly decrease performance as the memory controller has to figure out how many bits needs to go in which RAM stick (64 or 128 or 256), is this true?. I didn't even know that rank existed before you told me, thanks for that!

[porina]

1 hour ago, BenBRockN said:

I heard that mixing ranks (accidentally installing single & dual rank RAM) would significantly decrease performance as the memory controller has to figure out how many bits needs to go in which RAM stick (64 or 128 or 256), is this true?. I didn't even know that rank existed before you told me, thanks for that!

Don't know answer to that. I'd avoid it by only adding ram in matched pairs in systems where performance matters.

[Imakuni]

4 hours ago, porina said:

I'm also frustrated by the lack of information. If you have the Kingston part number, you can look up its specification, which I've had to do myself.

A rather unorthodox solution I've used in the past was to browse through the QVL for a couple of motherboards, as some of those lists (Gigabyte, if I remember right) include the nimber of ranks along with the kit model.

 

It's not an ideal solution, but hey, it could work if all else fails.