MEMCLK frequency

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In this article, we have explored the idea of MEMCLK frequency also known as Internal and External Memory Clock or MCLK, how to set a custom value to MEMCLK using BIOS settings and much more.

Table of contents:

  1. What is MEMCLK?
  2. Change value of MEMCLK in BIOS
  3. Conclusion

What is MEMCLK?

MEMCLK stands for Internal and External Memory Clock. MEMCLK Frequency is the frequency for DDR memory in the system. It is Memory clock on DDR4 memory is known as Data Rate. It has values like 1600 MT/s.

The Physical Clock in an AMD system is known as MEMCLK. These values are used for RAM Overclocking.

Memory clock is usually half of Data Rate as the speed of data transfer is twice the speed of I/O transactions on DDR.

So, if MEMCLK frequency is 1600 MT/s, then Data Rate is 3200 MT/s.

RAM frequency = 2 x MEMCLK frequency

In DRAM configuration High Register, the first 8 bits are related to MEMCLK values. These are as follows:

Bits Mnemonic Function
0 to 2 MemClkFreq Memory Clock Frequency
3 MemClkFreqVal Memory Clock Frequency Valid
4 to 7 MaxAsyncLat Maximum Asynchronous Latency

Depending on the system, the values of MemClkFreq are represented as follows:

  • 000b = 200 MHz
  • 001b = 266 MHz
  • 010b = 333 MHz
  • 011b = 400 MHz
  • 1xxb = reserved

Note: If MEMCLK frequency is 400 MHz, then Data Rate becomes 2 x 400 = 800 MHz.

Change value of MEMCLK in BIOS

To change the value of MEMCLK frequency using BIOS settings, follow the following steps:

  • Enter BIOS: While your system starts, press "delete" key to enter BIOS settings. The key varies across systems.
  • Once you enter BIOS, go to the following options to set Clock Frequency to Manual mode.
Advanced -> AMD CBS -> NBIO Debug Options -> XFR Enhancement -> Manual

By default, it is set to "Automatic" so the options to set frequency values are not available. Once you have set the above option to "Manual", you can set different CPU frequency values.

The next step is to set the MEMCLK Frequency. Follow the following steps:

Advanced -> AMD CBS -> NBIO Debug Options -> XFR Enhancement -> MEMCLK Frequency

Enter the desired frequency value manually. Note that the values are in hexadecimal.


Other clocks available in an AMD system beyond MEMCLK are:

  • CCLK: CPU Core Clock
  • FCLK: Data Fabric Clock (which is equal to Memory Clock)
  • UCLK: Internal Memory Controller Clock

MEMCLK frequency is a tunnable setting which is mainly used for RAM Overclocking. You should try to set it to different values in the BIOS settings and try which value works best for you.