Increase RAM speed in BIOS

DJViking wrote: I changed the XMP from Auto to "XMP 2.0 Profile 1", then the DDR Frequency was set to DDR4-3603. This had dramatic effect on my CPU. The CPU frequency dropped from 3600MHz to 2600MHz. I tried to set various memory speed in UEFI and the higher speed I choose the lower frequency I got on the CPU. After I changed XMP the memory frequency increased from 2133MHz to 2745MHz However running dmidecode in Linux it could only see 2 of 4 memory modules. Handle 0x0018, DMI type 17, 40 bytes Memory Device         Array Handle: 0x000F         Error Information Handle: Not Provided         Total Width: 72 bits         Data Width: 72 bits         Size: 8192 MB         Form Factor: DIMM         Set: None         Locator: DIMM_D1         Bank Locator: NODE 1         Type: DDR4         Type Detail: Synchronous         Speed: 2745 MHz         Manufacturer: Undefined         Serial Number: 00000000         Asset Tag: DIMM_D1_AssetTag         Part Number: F4-3600C17-8GTZ             Rank: 1         Configured Clock Speed: 2745 MHz         Minimum Voltage: Unknown         Maximum Voltage: Unknown         Configured Voltage: Unknown I changed the XMP back to Auto and everything was fine, but I want my memory to run at higher speed and preferably at 3000MHz without speed impact on the CPU.

As wardog mentioned, on the X99 platform, memory speeds at 3000 or above likely set the systems BCLK to 125MHz, from the standard 100MHz. That was done when you selected the XMP profile. The BCLK speed should be shown on the same screen as the XMP option setting. Did you notice what the BCLK speed was after selecting the XMP profile? This remains a mystery that you need to verify for us.

Also, we need the FULL model number of your memory to verify compatibility.

That BCLK frequency is shared by the CPU and memory, both use it with their own multipliers to produce their resulting speeds. The BCLK speed X the multiplier = Speed of CPU or DRAM.

Your CPU has a base clock speed of 3.6GHz. That means the base clock CPU multiplier is 36. 36 X 100MHz = 3,600MHz, or 3.6 GHz.

If the BCLK is 125 MHz, with the same CPU multiplier of 36, results is 36 X 125MHz = 4,500MHz, or 4.5GHz. That is a high over clock for a Broadwell-E processor.

You never asked why the CPU speed was reduced when you enabled the XMP profile. That seems to indicate you don't understand how the BCLK and multipliers work.

What is happening is the UEFI/BIOS detects the high CPU OC with the BCLK at 125MHz, and is setting the CPU multiplier lower to compensate. Actually, the numbers you gave us don't work out with a 125MHz BCLK speed, since I suspect your DDR4 memory is designed for use with Skylake CPU and chipset systems, which will NOT use a BCLK of 125MHz. Regardless, your board's UEFI must be reducing the CPU multiplier for some reason, if that is even correct.

That could be possible due to the use of Linux. There is essential Intel software that you don't have installed, since it is not available for Linux. That would be the Intel Management Engine (IME) software, that provides among other things communication between the board's firmware (UEFI/BIOS) and the OS.

Yet another situation is, your boards Memory Support List does not include memory above a speed of 3000. DDR4 memory at 3600 will be really, really pushing it for an X99 system, and certainly 32GB will be extremely difficult to maintain at that speed. I really should say impossible. As you have already seen, at a memory speed of 2745, only two of the four DIMMs were detected. That indicates the memory speed and/or the latency settings and DRAM voltage are not optimally set.

We must have the full model number of your memory, the BCLK value resulting from using the XMP profile, and the CPU multiplier that you get in the OC Tweaker screen CPU Configuration section, when you enable the XMP profile.

You could provide UEFI screen shots by putting a USB flash drive in a USB 2.0 port on the board's IO panel, and when in the UEFI UI, pressing the F12 function key, which will save an image of what is shown on the monitor as a file on the flash drive. You could then include those pictures in your next post.

I changed the XMP from Auto to "XMP 2.0 Profile 1", then the DDR Frequency was set to DDR4-3603.