4 of the DDR3 Serial Presence Detect (SPD) document (SPD4_01_02_11) adds support for Load Reduction DIMMs and also for 16b-SO-DIMMs and 32b-SO-DIMMs. JEDEC Solid State Technology Association announced the publication of Release 4 of the DDR3 Serial Presence Detect (SPD) document on September 1, 2011. XMP extension Intel Corporation officially introduced the eXtreme Memory Profile (XMP) Specification on March 23, 2007, to enable enthusiast performance extensions to the traditional JEDEC SPD specifications for DDR3 SDRAM. Variants In addition to bandwidth designations (e.g. DDR3-800D), and capacity variants, modules can be one of the following: ECC memory, which has an extra data byte lane used for correcting minor errors and detecting major errors for better reliability. Modules with ECC are identified by an additional ECC or E in their designation. For example: "PC3-6400 ECC", or PC3-8500E. Registered or buffered memory, which improves signal integrity (and hence potentially clock rates and physical slot capacity) by electrically buffering the signals with a register, at a cost of an extra clock of increased latency. Those modules are identified by an additional R in their designation, for example PC3-6400R. Non-registered (a.k.a. "unbuffered") RAM may be identified by an additional U in the designation. Fully buffered modules, which are designated by F or FB and do not have the same notch position as other classes. Fully buffered modules cannot be used with motherboards that are made for registered modules, and the different notch position physically prevents their insertion. Load reduced modules, which are designated by LR and are similar to registered/buffered memory, in a way that LRDIMM modules buffer both control and data lines while retaining the parallel nature of all signals. As such, LRDIMM memory provides large overall maximum memory capacities, while addressing some of the performance and power consumption issues of FB memory induced by the required conversion between serial and parallel signal forms. Both FBDIMM (fully buffered) and LRDIMM (load reduced) memory types are designed primarily to control the amount of electric current flowing to and from the memory chips at any given time. They are not compatible with registered/buffered memory, and motherboards that require them usually will not accept any other kind of memory. DDR3L and DDR3U extensions The DDR3L (DDR3 Low Voltage) standard is an addendum to the JESD79-3 DDR3 Memory Device Standard specifying low voltage devices. The DDR3L standard is 1.35 V and has the label PC3L for its modules. Examples