[SOLVED] Memory Speed Confusion; what's max speed?

[box o rocks]

I have an i7-6700 in an Asus Prime Q270M-C motherboard. I'm trying to decide what is the max speed DDR4 I can use.

1. Intel limits the CPU to 2133 MHz max
2. The motherboard limits the speed to 2400 MHz max...
3. while the board's BIOS allows up to 4266 MHz as max:

Which limit do I go by? I'm confused. I want to use the fastest RAM I can.

 

[Nine Layer Nige]

According to the Asus website, that board supports XMP, so it should simply be a case of switching on XMP (somewhere in the BIOS menu) and let the BIOS decide what is the fastest stable speed.
What RAM sticks do you have ? (make model)

 

[rgd1101]

depend on the cpu 6th gen is 2133, 7th is 2400

 

[SkyNetRising]

Which limit do I go by? I'm confused. I want to use the fastest RAM I can.

With i7-6700 on this board max frequency available is 2133mhz.
But you can use 3200mhz ram. It will just function at 2133mhz.

 

[box o rocks]

According to the Asus website, that board supports XMP, so it should simply be a case of switching on XMP (somewhere in the BIOS menu) and let the BIOS decide what is the fastest stable speed.
What RAM sticks do you have ? (make model)

I have 2133 MHz in the board now. And if there is an XMP option, I haven't found it. Maybe XMP only shows up if the RAM is XMP aware? My stuff is plain old generic RAM (single sided).
2xKingston and 2x Samsung.

 

[box o rocks]

Update:
OK. Went and temporarily removed a couple sticks of 3200 MHz XMP RAM from... another computer. 🙄 The XMP option appeared in my BIOS this time. But any speed faster than 2133 would either default back to 2133 or fail to boot. Looks like rgd1101 and SkyNetRising were right.

I guess I'll learn to live with 2133 MHz @ 16-18-18-36, unless anyone thinks I can tighten up timings with low cost RAM.

But that presents another question; why have all those XMP speeds available in BIOS if the board only supports 6th and 7th gen processors 🤔

 

[SkyNetRising]

why have all those XMP speeds available in BIOS if the board only supports 6th and 7th gen processors 🤔

Probably same BIOS version gets used on some other boards, that support ram overclocking (boards with chipset Z270).