SPD Parsing

Most DDR DIMM modules embed information about them which describes the timing, size and orientation, and manufacturing information of the device. The encoding of this information changes with each generation of the DDR devices and has its own format. The library attempts to normalize information across generations where possible.

The function libjedec_spd(3JEDEC) provides an interface to parse a full data payload into a nvlist_t, a name-value pair list usable with libnvpair(3LIB).

Currently DDR3, DDR4, DDR5, LPDDR3, LPDDR4, LPDDR4X, LPDDR5, and LPDDR5X are supported.

Vendor ID Translation

JEDEC Vendor IDs come as a pair of a continuation number and an index into a block. These are then translated into well-known names by the JEDEC standard JEP106 (Standard Manufacturer's Identification Code). This vendor information can be found in different contexts such as SPD data, various SPI NOR and SPI NAND devices, SMBIOS, and more.

The function libjedec_vendor_string(3JEDEC) provides the ability to translate the IDs to a well known name.

Currently the library implements JEP106BH from September 2023.

Temperature Ranges

Many JEDEC standards embed information about temperature ranges that components support for the case operating temperature, the ambient air temperature, and related. These ranges are in turn defined in JESD402-1B (Temperature Range and Measurement Standards for Components and Modules).

The function libjedec_temp_range(3JEDEC) provides a way to translate these named ranges into the corresponding lower and upper bounds of the range. When other parts of the library parse data, they will emit the temperature range using the library's libjedec_temp_range_t type, which is defined in the aforementioned manual page.