2 sticks or 4 for 32GB on Z370?

[GamingDaemon]

Hello!

So my 8700K shipped today, and I need a motherboard and memory. I know the Z370 is dual channel but, I see so many Coffee Lake builds on YouTube using 4 sticks of memory. The prices aren't that much different.

So 2 sticks of 16GB? or 4 of 8GB?

Corsair Memory

Thanks in advance!

 

[VirtualLarry]

If you want high memory clocks, then you're going to want to use less DIMMs overall.

 

[GamingDaemon]

Hmmm... So I do want to overclock the 8700K a little bit, but not a whole lot. So 3000Mhz or 3200Mhz memory speeds would be all I'd need, I think?

4 RGB sticks would look cooler in my open TT Core P3 Snow case, especially the G.Skill Trident Z RGB ones.

But I've heard 4 sticks of memory on a dual channel board can stress the CPU

So maybe I just get two??

Something like this:

https://ibb.co/fTOmAw

 

[BonzaiDuck]

Hmmm... So I do want to overclock the 8700K a little bit, but not a whole lot. So 3000Mhz or 3200Mhz memory speeds would be all I'd need, I think?

4 RGB sticks would look cooler in my open TT Core P3 Snow case, especially the G.Skill Trident Z RGB ones.

But I've heard 4 sticks of memory on a dual channel board can stress the CPU

So maybe I just get two??

Something like this:

https://ibb.co/fTOmAw

Generally, I agree totally with Larry. And I say "Do it when you first build the system, even if you think you are buying more GB of RAM than you need."

On the other hand, I'm not sure that the myth about stress from 4 sticks is worth the worry.

I started with 16GB, and agonized later over replacement with a 2x16=32GB kit, versus adding a duplicate kit of the original 16GB. I finally decided to go "cheap" as RAM prices were going up, and bought the 2x8GB=16GB kit. These were G.SKILL TridentZ DDR4-3200 14-14-14 sticks. G.SKILL had told me they "couldn't support 2 x (2x8GB) with unmatched kits of the same model" for purpose of warranty replacement for not meeting the spec of an individual 2x8 kit, but would support the RMA if the user could accept clocking the RAM to 3,000.

So I decided to roll the dice. The two kits work fine together at the XMP spec. Further, on the issue of stress to the CPU's IMC, I believe I had to change the VCCIO from "auto" to 1.18V. That is, the BIOS monitor had shown the "auto" value to be 1.16, and I changed the setting so the monitor showed 1.18V. 20mV shouldn't make a hilla-beans difference for the IMC, which has a spec limit of ~ 1.25V for my Skylake. Consider that you are using an i7-8700K. Other indications suggest taking the SA or System Agent voltage off "auto" as well, under a similar spec. And those indications suggest that "auto" will increase VCCSA excessively under the overclock scenario. This -- I didn't observe, but the spec limits are approximately the same for the two voltages.

So add the caveat that VCCIO (and possibly VCCSA) need to be tweaked slightly.

ALL THAT BEING SAID . . . . You shouldn't have to change anything from the original XMP settings -- you should not have to tweak the voltages -- for a 2x16GB=32GB kit.

In addition, with a 2x16 kit, you should be able to run them at a CR or command-rate of 1 instead of the default CR=2, although you might indeed have to tweak VDIMM, VCCIO or both slightly to make that work. But you can't so easily set CR=1 for a 4x8 kit.

Since the 8700K is a current-gen processor, you might want to consider a RAM speed higher than 3200, but 3200 should certainly be fast enough.

At today's prices, though, you are going to pay -- either for a 2x16 kit or a 4x8 kit.

 

[GamingDaemon]

Thank you BonzaiDuck! Wow, that's a lot to unpack.

So yes, 4x8GB is ~$430 and 2x16GB is ~$520. From both a money and aesthetics perspective, 4x8GB is the more attractive option. And some slight voltage increases doesn't sound too bad.

So then it comes down to whether the speed / performance is more important? Do I want CR=1 and potentially higher overclocking with 2 sticks?. Is that more important than the money and aesthetics of 4 sticks?

How much will CR=1 improve my perf? Will I be shooting the 6C/12T 8700K in the foot with slower memory speeds with 4 sticks? Will it even show up as extra frames in games?

 

[GamingDaemon]

After much anguish, went with these:

G.Skill 4x8GB Trident Z RGB 3000 15CAS $435

 

[GamingDaemon]

And here's my reasoning summed up nicely in a review of the Gigabyte AORUS Gaming 7 motherboard I plan to buy:

For Coffee Lake (8th Gen Intel procs) DDR4 may be clocked a notch faster at 2400 MHz as per Intel reference. We always say, volume matters more than frequency. A 3,200 MHz kit for example is far more expensive and does offer better bandwidth but the performance increases in real-world usage will be hard to find. Unless you transcode videos over the processor a lot. As always, my advice would be to go with lower clocked DDR4 memory with decent timings, but get more of it. Don't go for 8 GB, get four DIMMs and in total a minimum of 16 GB. The reason we test at 3200 MHz is simple, we do the same for AMD Ryzen and want to create a fair and equal playing ground for both.