Ram speed.

[estafano]

So the i7 9700k supports up to 2666 Mhz. Is that good?

[OfficialTechSpace]

No, but it does actually support higher. Intel just doesn't advertise that it does.

 

You could run a 3200Mhz kit or higher just fine.

[Levent]

Pretty sure it can run more than that, Intel certifies them up to 2666mhz and K series CPUs can overclock rams when combined with Z series chipset (this changed after this generation).

[estafano]

Just now, Levent said:

Pretty sure it can run more than that, Intel certifies them up to 2666mhz and K series CPUs can overclock rams when combined with Z series chipset (this changed after this generation).

Ohh okay so I should get something like 3200Mhz

[Mister Woof]

That's just the spec. If you put it in a non-Z series board, that's all it will do at maximum. If you put it in a Z-series board, it will do as fast as all three components (RAM, CPU memory controller, and motherboard) can support, which can vary, but nothing above 2666 is guaranteed. Higher speeds need more tweaking.

 

DDR 2666 is pretty slow by today's standards. DDR 3200 is almost guaranteed in practice. DDR 3600 is a safe bet. Speeds higher than 4000 take more work and tweaking and are less likely to work easily.

[estafano]

1 minute ago, Mister Woof said:

That's just the spec. If you put it in a non-Z series board, that's all it will do at maximum. If you put it in a Z-series board, it will do as fast as all three components (RAM, CPU memory controller, and motherboard) can support, which can vary, but nothing above 2666 is guaranteed. Higher speeds need more tweaking.

 

DDR 2666 is pretty slow by today's standards. DDR 3200 is almost guaranteed in practice. DDR 3600 is a safe bet. Speeds higher than 4000 take more work and tweaking and are less likely to work easily.

So would a Z390 work for me?

[Mister Woof]

1 minute ago, estafano said:

So would a Z390 work for me?

Yes, that's the Z series board that was released for the 9th gen CPUs. 

 

3200 should work with just XMP 99% of the time, 3600 probably also with just XMP (maybe some SA voltage), and 3800+ should work with extra SA and DRAM voltage (probably).

[estafano]

2 minutes ago, Mister Woof said:

Yes, that's the Z series board that was released for the 9th gen CPUs. 

 

3200 should work with just XMP 99% of the time, 3600 probably also with just XMP (maybe some SA voltage), and 3800+ should work with extra SA and DRAM voltage (probably).

I was also wondering how much ram I should get 16 or 32 and if I could buy it used

[Mister Woof]

8 minutes ago, estafano said:

I was also wondering how much ram I should get 16 or 32 and if I could buy it used

You'll get a couple of different answers:

 

1. All you need is 16; more memory won't make your games faster.

2. 16 is the minimum and some games can break above that, so get 32.

3. You don't really need more than 16, but if you have 2x8 single rank chips, getting 4x8 single rank chips is like dual rank chips which offers a small performance increase.

 

I think all of them are right to a degree, but since there's some small benefit from having 32 in a 4x8 configuration, and if you consider 16 is probably enough, saturating all 4 DIMMS won't harm you in the long run for upgrades anyway and RAM itself is a very small expense in the world of $1000 GPUs, I'd get a decent 4x8 kit (which is almost always single rank) or a known dual rank (since not all 16gb DIMMS are dual rank) 2x16 kit.

 

But be aware that it can sometimes be more difficult to run all DIMMS populated at higher speeds.

 

My 8700k at 5ghz and 4.7ghz cache manages DDR 3200 easily in 4x8, and my 10900KF managed DDR4 4000 pretty easily at 4x8 as well.

 

But, it depends, and generally the gains are relatively small unless you're SEVERELY CPU limited and even then only in some scenarios, not all.