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Serial presence detection (SPD) is a protocol used by computers to automatically configure the memory system during POST. Modern BIOS systems allow users to change settings and improve memory performance, including overclocking. Third-party programs can also alter default SPD information for performance changes.
Serial presence detection (SPD) is a protocol used by computers to automatically determine the correct settings to use for the computer’s memory system. During the power-on self-test (POST), the computer’s basic input/output system (BIOS) connects to the SPD. They exchange vital memory-related information and the BIOS automatically configures the system. For many years, it was difficult to change the information sent during SPD, but many modern BIOS systems have built-in features that allow users to change settings and tune memory performance. Serial presence detection is an improvement over the previous form of automatic configuration, parallel presence detection.
When a computer performs POST, it reads profiles of all hardware running on the system. Determine basic machine capabilities and specifications in order to set a stable profile for the hardware. As the boot process continues, this profile is used by the operating system and thus by applications to determine how they will run.
The settings on a modern memory module can be quite complex. There are a number of different parameters that must work together to keep the hardware stable. Manufacturers determine the correct settings for these factors and insert the profile into the serial presence detection chip.
The serial presence sensing module on a piece of computer memory is usually found on one end inside a tiny chip. This computer chip is separate from the rest of the chips on the module. In most cases, this chip will contain all of the memory-relevant hardware information, but will usually have space to store additional information if needed.
This extra space may be empty or may contain non-essential information available to the user. One of the most common pieces of information is about improving memory performance, a process called overclocking. When the initial memory profile is put together, it is very conservative. The profile is set far below the actual capacity of the hardware to ensure its stability.
In the past it was very difficult to change the information sent by the serial presence detection system. On modern computers, overclocking has become so commonplace that the methods are built right into the BIOS. The sub-profiles contained in a serial presence detection chip will often have completely different settings, allowing overclockers to simply choose a new profile if they choose.
In addition to changing the information in the BIOS, you can alter the default information sent by the SPD system. Depending on the type of computer hardware and memory manufacturer, it is possible to download third-party programs that will allow a user to change their SPD information. This will change the default settings sent to the BIOS during POSTing, resulting in major performance changes.
