Advanced Micro Devices (AMD) is marketing support for load reduced DIMM DD3 main memory for x86 and possibly all sorts of servers. It is churning out Inphi, the maker of the isolation memory buffer chip that is at the heart of this technology.
With LRDIMM memory you remove the register on a DDR3 memory module and add in a buffer chip that will allow the memory chips on the module to run at a higher clock speed and also allow for more memory chips to be put on each channel.
Last November when the Opteron 4200s and 6200s were released, AMD stated it would support registered, unregistered and load reduced DDR3 memory modules with the chips. In order to add LRDIMM support the main memory controllers of the Opterons had to be adjusted so they could compute the new chatter and support the higher clock speeds on the memory. The extra memory offered by AMD is only available through the use of LRDIMM memory.
According to the director of product marketing for server, embedded, AMD FireStream products at AMD – if you use unregistered DIMMs you top out at 64Gb per socket and with registered DIMMs reach 256GB per socket as an upper limit. This is twice the maximum memory as the prior generation of Opteron 6100 processors. When you move to LRDIMMs you can boost that memory capacity to 384GB per socket without having to resort to special memory extender electronics that add costs to the server.
Currently AMD have put the Inphi iMB buffer chip through their testing phase and have certified it as compliant with its Opteron 6200s. The Opteron 4200s can technically support the LRDIMM memory however, AMD doesn’t really expect customers to do that. But given the low-power server buyers and builders who like the Opteron 4200 chips and that for a given amount of memory the LRDIMMs burn less juice it is likely that customers will do just that.
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