{"product_id":"samsung-128gb-ddr4-2400-3ds-lrdimm-m386aak40b40-ctc","title":"Samsung 128GB 2400MHz DDR4 PC4-19200 ECC Registered CL17 288-Pin 3DS Load Reduced DIMM 1.2V Octal Rank x4 Memory Module - M386AAK40B40-CTC","description":"\u003cp\u003eThe Samsung M386AAK40B40-CTC is a 128GB DDR4-2400 LRDIMM for servers. It uses stacked memory chips, runs at 1.2V, and has 288 pins. The label reads 128GB 2S4Rx4 PC4-2400T-L, which sellers also write as 8Rx4.\u003c\/p\u003e\n\u003ch2\u003eHow 128GB fits on one stick\u003c\/h2\u003e\n\u003cp\u003eSamsung lists the module as (4H 3DS 8G x 4) x 36. That is 36 chip packages, and each package stacks four 8Gb dies. 3DS means three-dimensional stacking. The chip math works out like this.\u003c\/p\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eItem\u003c\/th\u003e\n\u003cth\u003eAmount\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eChip packages\u003c\/th\u003e\n\u003ctd\u003e36\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eDies in each package\u003c\/th\u003e\n\u003ctd\u003e4\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eSize of each die\u003c\/th\u003e\n\u003ctd\u003e8Gb\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eRaw memory\u003c\/th\u003e\n\u003ctd\u003e1,152Gb (144GB)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eData memory\u003c\/th\u003e\n\u003ctd\u003e128GB\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eECC check bits\u003c\/th\u003e\n\u003ctd\u003e16GB\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003eEight logical ranks of x4 chips share the 36 packages. That is why sellers call the module octal rank. The server sees a load that the buffer chips hide.\u003c\/p\u003e\n\u003ch2\u003eWhy LRDIMM\u003c\/h2\u003e\n\u003cp\u003eAn LRDIMM carries buffer chips that hide the load of all those memory chips from the controller. That lets a server hold more memory per channel. The trade is a little extra latency and some added power.\u003c\/p\u003e\n\u003ch2\u003eSpeed and fit\u003c\/h2\u003e\n\u003cp\u003eThe module runs at 2400 MT\/s with CL17, which moves 19.2 GB\/s. A server runs it at the lower of that speed and the CPU limit. It needs a server that takes DDR4 3DS LRDIMMs, so check your memory guide for 128GB support. It can't share a server with plain RDIMMs, and a desktop PC can't use it.\u003c\/p\u003e\n\u003cp\u003eTwelve modules give 1.5TB. Twenty-four give 3TB.\u003c\/p\u003e\n\u003ch2\u003eQuick answers\u003c\/h2\u003e\n\u003ch3\u003eIs it 8Rx4 or 2S4Rx4?\u003c\/h3\u003e\n\u003cp\u003eBoth names describe the same module: eight logical ranks of x4 chips.\u003c\/p\u003e\n\u003ch3\u003eWhat is a 4H stack?\u003c\/h3\u003e\n\u003cp\u003eFour dies stacked in one package and joined by tiny vertical links.\u003c\/p\u003e\n\u003ch3\u003eWhat does 8Gb x4 mean?\u003c\/h3\u003e\n\u003cp\u003eEach die holds 8 gigabits and talks to the module over four data lines.\u003c\/p\u003e\n\u003ch3\u003eWhy so many ranks?\u003c\/h3\u003e\n\u003cp\u003eStacking adds capacity without adding more chip packages to the board. That is how 128GB fits on a standard-size module.\u003c\/p\u003e\n\u003ch3\u003eDoes it match the CUC version?\u003c\/h3\u003e\n\u003cp\u003eThe part numbers differ by one letter. Match the suffix on your installed modules.\u003c\/p\u003e\n\u003ch2\u003eM386AAK40B40-CTC specifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eBrand\u003c\/th\u003e\n\u003ctd\u003eSamsung\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003ePart number\u003c\/th\u003e\n\u003ctd\u003eM386AAK40B40-CTC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eCapacity\u003c\/th\u003e\n\u003ctd\u003e128GB\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eType\u003c\/th\u003e\n\u003ctd\u003eDDR4 LRDIMM, 3DS\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eSpeed\u003c\/th\u003e\n\u003ctd\u003e2400 MT\/s (PC4-19200)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eBandwidth\u003c\/th\u003e\n\u003ctd\u003e19.2 GB\/s\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eRank\u003c\/th\u003e\n\u003ctd\u003e2S4Rx4 (8Rx4)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eCAS latency\u003c\/th\u003e\n\u003ctd\u003eCL17\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eDRAM\u003c\/th\u003e\n\u003ctd\u003e4H 3DS, 8Gb x4 dies\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003eVoltage\u003c\/th\u003e\n\u003ctd\u003e1.2V\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth scope=\"row\"\u003ePins\u003c\/th\u003e\n\u003ctd\u003e288\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e","brand":"Samsung","offers":[{"title":"Default Title","offer_id":62811035926899,"sku":"M386AAK40B40-CTC","price":1814.1,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0992\/9546\/1747\/files\/m386aak40b40-ctc.jpg?v=1778022151","url":"https:\/\/cpurepublic.com\/products\/samsung-128gb-ddr4-2400-3ds-lrdimm-m386aak40b40-ctc","provider":"CPU Republic LLC","version":"1.0","type":"link"}