I just heard from my contacts at JEDEC that they have issued Release 4 of the DDR3 Serial Presence Detect (SPD) Specification. Known as SPD4_01_02_11, Release No. 21A. SPD Annex K - Serial Presence Detect (SPD) for DDR3 SDRAM Modules, the new specifications cover three new memory module types. If you want a copy, it is avaialble for download here.
The new spec includes support for load-reduction DIMMs that are used in high-end computing and also for 16b and 32b SO-DIMMs that are used for embedded applications. JEDEC expects that modules using these new specs will be released by manufacturers next year.
What do you think? Any surprises here? Are you working with this spec and encountering any issues? Sound off below.
SPD is a method that is used by BIOS/boot firmware to identify the type of DRAM (in this case, DDR3 SDRAM) that is installed in the system.
Memory modules (DIMMs, SODIMMs) always have a small EEPROM device on them that contains data identifying the type of memory chips on the memory module. SPD governs the organization of the data on that EEPROM. This data is read by BIOS/boot firmware at boot time and is used to configure the chipset/memory controller.