Both Tandem DP2 and IBM Coupling Facility on zSeries Sysplexes worked exactly like how you envisage an SPU would work. Therefore, when we developed RDMA-attache

Both Tandem DP2 and IBM Coupling Facility on zSeries Sysplexes worked exactly like how you envisage an SPU would work. Therefore, when we developed RDMA-attached persistent memory at Tandem in 2002, we put it under the control of DP2/ADP process pairs. Later, we ported it to HP-UX and InfiniBand RDMA. There is one paper at IPDPS'04 and several published patents you can look up in my Google Scholar page. pmem.io crowd is reinventing some of this wheel. If any of you work at HPE, you can find much more detailed internal papers, source code, drivers, firmware, and other stuff that the outside world cannot get to.