Motherboard Memory Settings and "Meaning of XMP"

[BonzaiDuck]

I'm using G.SKILL 2x8GB Ripjaws "Z" "GZH" DDR3-1866 RAM, spec'd at 9-9-9-24-2n.

In my ASUS "tweaker" settings menu, there is an "Ai Tuner" menu which offers "Auto," "Manual" and "X.M.P."

I had previously -- variously chosen "Manual" and set the timings to spec and "Auto" with the timings set to the same spec.

What does "XMP" do? Does XMP affect all of the subsidiary timings -- which we usually leave on "Auto?"

 

[razel]

XMP are overclocked speeds/timings approved and tested by the manufacturer and are programmed into the RAM, if your RAM offers it.

 

[denis280]

XMP are overclocked speeds/timings approved and tested by the manufacturer and are programmed into the RAM, if your RAM offers it.

This

 

[VirtualLarry]

Setting XMP on certain mobos will enable an auto-overclock, or multi-core turbo. Even though it should be just for the memory.

 

[BonzaiDuck]

I had never selected the "XMP" option before as a choice for continued operation. I don't know why. I just felt more comfortable keying in the spec settings of the RAM -- the basic timings -- manually.

I think one time I tried that selection, and inadvertently overclocked the RAM. Didn't mess with it anymore; went back to "Manual" or "auto" and the spec timings.

This time, I must have picked the right settings to "go with" the XMP setting, because the RAM is running at its spec 1866 Mhz and 9-9-9-24-2n

 

[nenforcer]

I think it stands for "eXtreme Memory Profile" or something to that effect. It lets you auto over-clock your memory to the setting approved or specified by the manufacturer.

 

[BonzaiDuck]

I think it stands for "eXtreme Memory Profile" or something to that effect. It lets you auto over-clock your memory to the setting approved or specified by the manufacturer.

In other words, if motherboards "default" to DDR3-1333 for either 1600 or 1866-rated RAM, you would have to set the RAM manually -- this had been discussed many times and I see the annoyance of customer-reviews at Egg, complaining that the high-speed RAM runs as 1333.

Maybe I'm mistaken, but I think you're saying that XMP handles this problem. Or maybe we're talking about "what overclocked means" for RAM. If the RAM was spec'd at 1866, I wouldn't think of it as "overclocked", but that's what the motherboard specs show about memory-speed compatibility, when they specify something like "1866 (OC)."

 

[denis280]

In other words, if motherboards "default" to DDR3-1333 for either 1600 or 1866-rated RAM, you would have to set the RAM manually -- this had been discussed many times and I see the annoyance of customer-reviews at Egg, complaining that the high-speed RAM runs as 1333.

Maybe I'm mistaken, but I think you're saying that XMP handles this problem. Or maybe we're talking about "what overclocked means" for RAM. If the RAM was spec'd at 1866, I wouldn't think of it as "overclocked", but that's what the motherboard specs show about memory-speed compatibility, when they specify something like "1866 (OC)."

Yes it is.some board will run default 1333.then you have to set your XMP to the ram specification.

 

[Topweasel]

It's not overclocking the sense of the rated speed of the chips. Jedec only specs up 1333 for any speed higher then that you have to manually set the performance by hand. XMP was created to allow the boards detect its rated rate if its higher than 1333. You are not OCing the memory stick as much as you are using XMP to run the stick at the speed the manufacturer advertised it.

 

[coffeejunkee]

Jedec specs are actually up to 2133MHz now. My cpu is rated for 1600MHz, and so is my ram but I still had to manually set it to 1600. Not sure why mobo manufacturers are sticking to 1333 default...

Just think of all the time and forum space saved if:
- ram manufacturers put a little warning on their products like "you need to manuallly set this memory to run at its rated speed"
- cpu-z showed double data rate speed
- Intel didn't publish tcase max on their site.

 

[Topweasel]

Jedec specs are actually up to 2133MHz now. My cpu is rated for 1600MHz, and so is my ram but I still had to manually set it to 1600. Not sure why mobo manufacturers are sticking to 1333 default...

Just think of all the time and forum space saved if:
- ram manufacturers put a little warning on their products like "you need to manuallly set this memory to run at its rated speed"
- cpu-z showed double data rate speed
- Intel didn't publish tcase max on their site.

Your right on the Jedec. But I was thinking more about when XMP launched than anything else. If I had to point anyone it would probably be Intel. By keeping the max autodetect as low as possible they can have the memory manufacturers use XMP for the higher settings. Since XMP is Intel only when the memory is used in an AMD machine it won't run at the high settings it was sold at and either the builder doesn't notice or they spend hours testing all the timings to make it stable. Probably hoping that the tech then decides to go Intel because it's so much easier to setup.

 

[BonzaiDuck]

The only settings exposed in the BIOS with the XMP setting are the basic four latencies and the command rate. But that's no guarantee that XMP doesn't affect other timings that aren't exposed in the BIOS.

There is a fairly recent Anandtech article, urging readers to choose XMP in BIOS. Yet, other opinions deride it as a crutch for noobie-noob mainstreamers and beginners. Somehow, the Anandtech article vaguely insinuates that XMP provides an optimum memory configuration.

Also, here's another thing someone might answer -- although I've already submitted my e-mail question to G.SKILL. In my sig, I show the Ripjaws Z 1866 ". . GZH" 2x8GB kit with the black heatspreaders.

I had previously set my VCCIO at a fixed value -- variously below 1.15 and above 1.08V. This is a two-module kit -- albeit 16GB. With XMP at spec (or even manual settings of spec timings), you would think you could simply run VCCIO as "Auto". Auto would likely give an effective value < 1.0V. I had turned up the VCCIO previously because (a) I was running DDR3-1600 G.SKILL Ripjaws GBRL RAM at 1866, and -- (b) I was using two kits and populating all four slots.

Somewhere -- some other forum site -- somebody mentioned boosting the VCCIO if you were over-clocking the processor. I HAVE overclocked the processor -- been running that way since I built it.

But do I NEED to manually set a higher VCCIO for a 2x kit running at spec timings and voltage, even if the processor clock is higher? My bCLK setting is "stock" at 100.