Comment by sudosysgen

There are DDR4 interposers you can buy for 50$. The basic thing is that you don't need all of the ram all of the time, you just need to find an address which you can then rewrite to make two valid references to the same physical memory (see: badRAM/battering ram). Then you can use an IOMMU compliant DMA to access that memory.

Or you can use an FPGA to interpose the RAM and intercept the network traffic for a couple hundred bucks.