Wi-Fi | Software: A brief discussion on modifying DDR frequency through CDT in Qualcomm IPQ series

Overview of Double Data Rate (DDR) Memory Technology and Frequency Adjustment Methods

Introduction to DDR Memory Technology

Double Data Rate (DDR) is a technology widely used in computer random access memory (RAM) modules. Its main feature is the ability to transfer data on both the rising and falling edges of the clock cycle, achieving higher performance compared to traditional Single Data Rate (SDR) memory. DDR technology has undergone multiple generations of evolution, with each generation offering improvements in speed, capacity, and power consumption.

1. DDR1The earliest DDR technology has now been phased out.
2. DDR2Speed increased, power consumption reduced.
3. DDR3Features higher frequency and lower voltage.
4. DDR4Currently mainstream, fast speed, large capacity, and low power consumption.
5. DDR5The latest generation further enhances speed and capacity, making it suitable for high-performance computers and servers.

DDR4 Memory Specification Example

Here are some example specifications of DDR4 memory modules:

DDR frequency adjustment method

In certain situations, the system may not function properly, which could be related to mismatched DDR memory frequency settings. The following uses Qualcomm's IPQ series chips as an example to explain how to adjust DDR frequency by modifying the CDT (Configuration Data Table) file.

1. Verify memory specifications

Taking ESMT's M16U4G16256A as an example, its specification is 256M16. The reference design uses two DDR chips, which together connect to DQ[0..31], totaling 32 bits.

2. Reference Documents

According to the document "80-YB714-1_REV_YB_CDT_Definition_and_Memory_Configuration_for_WLAN_AP_Chipsets_User_Guide.pdf," the parameter file used by AP-AL05 is 256M32_DDR4.xml.

3. Adjust frequency settings

In the 256M32_DDR4.xml file, locate the boot_settings section of cdb2 and adjust the following fields:

For example, change the 14:13 position of the original value 3918 to b01, and the new value after conversion will be 12110.

4. Update firmware

1. Save the modified 256M32_DDR4.xml file.

2. Execute the following commands to regenerate cdt.bin and create a single image file:

   

3. Use tftpboot to update the firmware.
4. Restart the system and verify if the DDR frequency has been changed to 1333 MHz.

Frequently Asked Questions

1. Why is it necessary to adjust the DDR frequency?
   Answer: When the system is not functioning properly, it may be due to the DDR frequency settings not matching the hardware specifications. Adjusting the frequency can resolve this issue.
2. How can I confirm if the changes were successful?
   Answer: After restarting the system, you can check the DDR frequency in the console log to see if it is displayed as the configured value (e.g., 1333 MHz).
3. Is there any risk in modifying CDT files?
   Answer: If modifications are not done properly, it may result in the system failing to start. Therefore, it is recommended to back up the original files before making any changes.
4. Do all DDR memory modules support frequency adjustment?
   Answer: Not all memory modules are supported; it is necessary to verify whether the hardware specifications and chip design allow it.
5. Is the Qualcomm IPQ series chipset compatible with other DDR technologies?
   Answer: Qualcomm IPQ series primarily supports DDR3 and DDR4 technologies. Specific support details should be referred to in the chip specification documents.

Reference materials

1. 《80-YB714-1_REV_YB_CDT_Definition and Memory Configuration for WLAN AP Chipset User Guide.pdf》
2. 《80-19574-10_REV_AW_IPQ95XX_Approved Supplier List.pdf》

The above provides a detailed explanation of DDR memory technology and frequency adjustments, hoping to help you resolve related issues and enhance system performance.