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What speed is my RAM, really?

Posted: Sat Nov 07, 2020 8:55 pm
by Yan
I've bought some DDR4-3000 RAM. I've set the memory's speed to 3000 MHz in the BIOS manually.

Windows reports that my memory is running at 3000 MHz, and the "Memory" tab in CPU-Z reports 1499.1 MHz, which I believe is correct.

However, the "SPD" tab in CPU-Z reports DDR4-2132. Who's telling the truth?

If I let my BIOS set the memory speed automatically, then everybody agrees it's running at 2133 MHz.

I've run MemTest 86+ and it's found no errors. The BIOS is up to date.

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BankLabel  Capacity    Caption          CreationClassName     DataWidth  Description      DeviceLocator  FormFactor  Manufacturer   PartNumber         Speed
BANK 1     8589934592  Physical Memory  Win32_PhysicalMemory  64         Physical Memory  DIMM_A2        8            G-Skill       F4-3000C16-8GISB   3000         
BANK 3     8589934592  Physical Memory  Win32_PhysicalMemory  64         Physical Memory  DIMM_B2        8            G-Skill       F4-3000C16-8GISB   3000

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Re: What speed is my RAM, really?

Posted: Sat Nov 07, 2020 9:04 pm
by JustAnEngineer
Your memory defaults to the JEDEC speed in the SPD. However, if you go into your motherboard's BIOS/UEFI setup and select XMP or DOCP, then you'll get the advertised speed. DDR4-3000 runs at 1500 MHz, with two signals per cycle. With 8 bits per signal per DIMM, you get your memory's rating of PC4-24000.

Re: What speed is my RAM, really?

Posted: Mon Nov 09, 2020 9:38 am
by Aranarth
Personally, I go by whatever CPU-Z tells me.

In your case, just under 1500mhz (x2) to get 3000mhz.
or rather 1499.1 x 2 = 2998.2mhz

Re: What speed is my RAM, really?

Posted: Mon Nov 09, 2020 2:45 pm
by Flying Fox
Aranarth wrote:
Personally, I go by whatever CPU-Z tells me.

In your case, just under 1500mhz (x2) to get 3000mhz.
or rather 1499.1 x 2 = 2998.2mhz

The OP was confused that the SPD tab (which is in CPU-Z!) appeared to be telling you otherwise.

Re: What speed is my RAM, really?

Posted: Mon Nov 09, 2020 3:36 pm
by just brew it!
Flying Fox wrote:
Aranarth wrote:
Personally, I go by whatever CPU-Z tells me.

In your case, just under 1500mhz (x2) to get 3000mhz.
or rather 1499.1 x 2 = 2998.2mhz

The OP was confused that the SPD tab (which is in CPU-Z!) appeared to be telling you otherwise.

Yup. And JAE explained the difference between SPD timings and actual timings.