README.md

Fixing falsely reported RAM speed in macOS

• About
• Fix
• Gathering RAM data
  • Using Windows
  • Using Linux (recommended)
• Add the memory data to your config.plist
• Verify
• Further Resources

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About

I recently acquired a Lenovo T490 Laptop. While checking the installed RAM, I noticed in System Profiler that the reported RAM speed was 2400 MHz:

But in Windows it was reported correctly, running @2666 MHz:

Since in Wintel systems RAM speed is are handle by the BIOS/UEFI Firmware, I assume there's a memory speed reporting issue in macOS.

Fix

In order to fix the falsely reported memory speed in macOS, you can do the following. I say can because this fix is purely cosmetic:

Gathering RAM data

Using Windows

1. Run Windows, open a command prompt and enter:

   wmic memorychip list full

2. The output shoul look like this:

   BankLabel=BANK 0
   Capacity=8589934592
   DataWidth=64
   Description=Physical Memory
   DeviceLocator=ChannelA-DIMM0
   FormFactor=12
   HotSwappable=
   InstallDate=
   InterleaveDataDepth=
   InterleavePosition=
   Manufacturer=Samsung
   MemoryType=0
   Model=
   Name=Physical Memory
   OtherIdentifyingInfo=
   PartNumber=M471A1K43BB1-CTD
   PositionInRow=
   PoweredOn=
   Removable=
   Replaceable=
   SerialNumber=00000000
   SKU=
   Speed=2667
   Status=
   Tag=Physical Memory 0
   TotalWidth=64
   TypeDetail=128
   Version=
   
   BankLabel=BANK 2
   Capacity=8589934592
   DataWidth=64
   Description=Physical Memory
   DeviceLocator=ChannelB-DIMM0
   FormFactor=12
   HotSwappable=
   InstallDate=
   InterleaveDataDepth=
   InterleavePosition=
   Manufacturer=Samsung
   MemoryType=0
   Model=
   Name=Physical Memory
   OtherIdentifyingInfo=
   PartNumber=M471A1K43CB1-CTD
   PositionInRow=
   PoweredOn=
   Removable=
   Replaceable=
   SerialNumber=397269CB
   SKU=
   Speed=2667
   Status=
   Tag=Physical Memory 1
   TotalWidth=64
   TypeDetail=128
   Version=
   

3. Save the data as a .txt file so you can access it later from within macOS

Using Linux (recommended)

Using Linux is recommended because the command used under Windows doesn't show the AssetTag. Listed below are the instructions to run a live version of Linux from a USB flash drive directly from an .iso, without needing to install Linux.

1. Prepare a USB Flash Drive with Ventoy
2. Download an .iso of a Linux distribution of your choice (for example Ubuntu or Zorin, etc.)
3. Copy the .iso to your Ventoy USB stick
4. Reboot from USB flash drive
5. In the Ventoy menu, select your Linux distro and click on "Normal Boot"
6. Select the "Try" option instead of the "Install" option
7. Once you've reached the Desktop, run Terminal and enter:

   sudo dmidecode -t memory

8. The output should look like this:

   dmidecode 3.2
   Getting SMBIOS data from sysfs.
   SMBIOS 3.1.1 present.
   
   Handle 0x0002, DMI type 16, 23 bytes
   Physical Memory Array
   	Location: System Board Or Motherboard
   	Use: System Memory
   	Error Correction Type: None
   	Maximum Capacity: 16 GB
   	Error Information Handle: Not Provided
   	Number Of Devices: 2
   
   Handle 0x0003, DMI type 17, 40 bytes
   Memory Device
   	Array Handle: 0x0002
   	Error Information Handle: Not Provided
   	Total Width: 64 bits
   	Data Width: 64 bits
   	Size: 8192 MB
   	Form Factor: SODIMM
   	Set: None
   	Locator: ChannelA-DIMM0
   	Bank Locator: BANK 0
   	Type: DDR4
   	Type Detail: Synchronous
   	Speed: 2667 MT/s
   	Manufacturer: Samsung
   	Serial Number: 00000000
   	Asset Tag: None
   	Part Number: M471A1K43BB1-CTD    
   	Rank: 1
   	Configured Memory Speed: 2400 MT/s
   	Minimum Voltage: Unknown
   	Maximum Voltage: Unknown
   	Configured Voltage: 1.2 V
   
   Handle 0x0004, DMI type 17, 40 bytes
   Memory Device
   	Array Handle: 0x0002
   	Error Information Handle: Not Provided
   	Total Width: 64 bits
   	Data Width: 64 bits
   	Size: 8192 MB
   	Form Factor: SODIMM	
   	Set: None
   	Locator: ChannelB-DIMM0
   	Bank Locator: BANK 2
   	Type: DDR4
   	Type Detail: Synchronous
   	Speed: 2667 MT/s
   	Manufacturer: Samsung
   	Serial Number: 397269CB
   	Asset Tag: None
   	Part Number: M471A1K43CB1-CTD    
   	Rank: 1
   	Configured Memory Speed: 2400 MT/s
   	Minimum Voltage: Unknown
   	Maximum Voltage: Unknown
   

9. Save the data as a .txt file on a USB flash drive so you can access it later from within macOS

Note

It seems that macOS displays the "Configured Memory Speed" value instead of the "Speed" value. And since the Configured Memory Speed is 2400 MT/s in my case, that's the reason why the reported speed is lower in macOS than in Windows. But "Configured Memory Speed" actually refers to the actual speed the RAM is running at and not the maximum possible speed it is capable of. This can be changed in BIOS but Laptop BIOSes usually don't let you configure RAM speeds. Mhh…

Add the memory data to your config.plist

⚠️ Read OpenCore's "Documentation.pdf", chapter 10.4: "Memory Properties" to get familiar with the available parameters before entering any data into your config.plist! Because some parameters use different values in OpenCore and have to be converted from hex to decimal.

1. Reboot into macOS
2. Run OpenCore Auxiliary Tools, mount the EFI and open your config.plist
3. Navigate to PlatformInfo/Memory
4. Enable CustomMemory (disabling it ignores the whole Memory section)
5. Enter the relevant data you gathered earlier and ensure it follows OpenCore's standards:
6. Save your config and reboot

Verify

• Run System Profiler
• Check "Memory" Section. The correct memory speed should be reported now:
  
• Done

Further Resources

• New Memory Properties Section by miliuco