Copying response send on original post. T640 support 2666 speed memory. T640 does not support 3200 MT/s memory. As you pointed out Kingston KTD-PE426D8/16G looks like have same specification of current one.  Looks like this one is not from Dell. In most of the cases we seen memory with same specification works but we can not guarantee that non Dell memory will work as it is not validated..  You can refer below link for more details on memory supported on T640 [URL] [URL] 
Currently we're using Dell PowerEdge T640 Server with Processor(s) Intel Xeon Silver 4210 2.2G, 10C/20T with 2x 16GB SKhynix 16GB 2Rx8 PC4 - 2666v-re2-12(HMA82GR7JJR8N-VK TF AC) Memory on it and 1 of the memory just crush down.So i decided to purchase 1 replacement for that memory and our supplier offer me this MemoryDell 16GB 3200 MT/s MemoryKingston KTD-PE426D8/16G Memory Which 1 of this memory is suitable for my server and does this memory can work together with our 1 remaining SKhynix 16GB 2Rx8 PC4 memory?Please if anyone can help me with thisBelow are links for memory specs: SKhynix 16GB 2Rx8 PC4 - 2666v -[URL] Kingston KTD-PE426D8/16G Memory [URL] Dell 16GB 3200 MT/s Memory[URL] PS This discussion was created because of my wrong posts last time.
Dell PowerEdge T640 Memory replacement. Need help and advice