Confused by mobo supported memory speeds

[spirigo]

Hi all,

I want to bow this mobo:

https://uk.pcpartpicker.com/part/asrock-motherboard-z170mpro4s

Buuuuut it has a strange memory support:

DDR4-2133 / 2400 / 2800 / 2933 / 3200

I kind want to get ddr4 2666 or 3000 because I'll be running on i3 6100 so does that mean the memory will be downclocked to 2400 and 2933 respectively?

It makes no sense tbh...

Please help!

Thanks

 

[Shaun o]

HI spirgo,

To answer your question when a motherboard states the speed range or value that it will except for DDR4 memory modules in the speed they run.

You are looking only at the minimum and maximum stated values of the speed range quoted.
Any Ram you buy that has a slightly off set value to the ones as a guide quoted on the specifications of the motherboard is Aceptable.

The memory, or the memory sticks you buy contain information on how your motherboard and it`s bios should auto set the values.

It means that if you choose, and the memory of the new sticks can be overclocked for example that you could reach the speed ratings quoted on the DDR4 listing of the speed of memory modules for the motherboard.

The speed ratings you see quoted can often be the XMP or overclocked ratings of memory the motherboard runs.
So when you look at memory for example say with a 2666Mhz value it can be the value without xmp memory mode enabled where as with the xmp mode enabled. it would in fact be 2800Mhz in speed.

Xmp mode is essentially a set mode of the bios that auto over clocks it, by enabling Xmp mode for memory in the bios of the motherboard. As said for example memory you see at 3000Mhz is likely the speed it runs at without Xmp mode disabled
Where as 3200Mhz will be with the Xmp mode enabled.

In Xmp memory mode about 200Mhz on average is increased on the speed of memory when enabled.
If you do the math each value equals the ones stated of the motherboard memory speeds, plus or minus about 40Mhz.

So it would say that the mix up is the values you quoted where not xmp enabled speeds.

 

[spirigo]

So basically that mobo will run ddr4 2666/3000 memory without underclocking it to 2400/2933?

 

[Shaun o]

Yes, but are the values you are looking at stock speed, or speed values with Xmp memory modes.
Because it looks like you are reading the stock speed values where as the Xmp enabled values of the memory.

Would be 2800Mhz and 3200Mhz. with Xmp mode enabled for both the 2666Mhz and 3000Mhz modules you intend to buy.

Post the link to the memory modules if you can, and i will check.

 

[spirigo]

Ahh I see, so the RAM has non xmp speeds stated while the mobo has the maximum xmp settings stated. Wow, I think I learnt something today! This is great.

But just to be sure here are the ram I am looking to get (either one or the other, haven't decided yet):

https://uk.pcpartpicker.com/part/corsair-memory-cmk8gx4m2a2666c16

or

https://uk.pcpartpicker.com/part/panram-memory-pud43000c154g2njk

Leaning towards the former because 2666 is enough to make i3 6100 operate very smoothly at high loads.