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为什么添加两个 dimm 卡后配置的时钟速度会发生变化

tag-icon • tag-icon memory redhat-enterprise-linux kernel
为什么添加两个 dimm 卡后配置的时钟速度会发生变化

我们有一台配备 DELL HW 的 Linux 机器，该机器有 256G 内存

在添加新的 32G DIMM 卡之前，我们已验证其Configured Clock Speed为 2400MHz

因此稍后我们为这台机器添加了额外的 32G（2 个 DIMM 卡，与机器已有的 DIMM 卡类型相同），并且在机器启动后，我们检查了它Configured Clock Speed，dmidecode发现它已经发生了变化

因此从Configured Clock Speed改为2400MHz1866 MHz

例子

添加新的 DIMM 之前

dmidecode | grep "Configured Clock Speed"
        Configured Clock Speed: 2133 MHz
        Configured Clock Speed: 2133 MHz
        Configured Clock Speed: 2133 MHz
        Configured Clock Speed: 2133 MHz
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: 2133 MHz
        Configured Clock Speed: 2133 MHz
        Configured Clock Speed: 2133 MHz
        Configured Clock Speed: 2133 MHz
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown

添加新的 DIMM 后

  Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: 1866 MHz
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown
        Configured Clock Speed: Unknown

那么造成这种变化的原因可能是什么呢？为什么通过添加一个 dimm 内存，然后就Configured Clock Speed发生了这样的变化？

Server is Dell PowerEdge R730 and memories are:

Memory Device
    Array Handle: 0x1000
    Error Information Handle: Not Provided
    Total Width: 72 bits
    Data Width: 64 bits
    Size: 16384 MB
    Form Factor: DIMM
    Set: 3
    Locator: A9
    Bank Locator: Not Specified
    Type: DDR4
    Type Detail: Synchronous Registered (Buffered)
    Speed: 2400 MHz
    Manufacturer: 002C0632002C
    Serial Number: 1B42681B
    Asset Tag: 001808A0
    Part Number: 18ASF2G72PDZ-2G3D1
    Rank: 2
    Configured Clock Speed: 1866 MHz
    Minimum Voltage:  1.2 V
    Maximum Voltage:  1.2 V
    Configured Voltage:  1.2 V

在此处输入图片描述

答案1

您的服务器有 2 组，每组有 12 个 DIMM 插槽。每组分为 4 个内存通道。每个通道中的前两个 DIMM 插槽支持高达 2400MHz 的速度，但第三个插槽仅支持 1866MHz。当您开始填充第三个插槽时，所有速度都会降至系统上的最低速度。有关更多详细信息，请查看用户手册。

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