Review on Ableconn PEXM2-130 Dual PCIe NVMe M.2 SSDs Carrier Adapter Card (ASMedia ASM2824 Switch) - High-Speed 2X M.2 NGFF PCIe NVMe SSD Support for Mac & PC (PCIe x8, Non-Bifurcation Motherboard) by Reynaldo Guzman

Timeouts occur when used in HP Z600, PCIe2. HP ensures sufficient power per slot and supports NVMe cards on single-connect risers. There are two 16x slots and two 8x slots (and two PCI32 slots). I installed two 2TB Intel NVMe cards in each Ableconn adapter. Each adapter plugs into a 16x slot. Linux kernel 4.19 is my main goal, but I also tested 5.7. Both see the NVMe devices, but they expire, go offline, have zero bytes, or are read-only. The second two show up in udev, but not the first two. It didn't matter whether I swapped slots or NVME between the cards. It was always two. If I only used one adapter, one of the slots, it wouldn't allow two NVMe devices. I've tried disabling or increasing default_ps_max_latency_us to no avail. I've tried moving them to 8x slots, also to no avail. (One of the PCIe x8 slots is Gen 1, so the AbleConn card showed promise.) I've found that the Ableconn adapters' heatsinks get hot, but there's enough airflow in this system. When I pulled out the NVME devices, plugged them into single module PCI slot adapters, and plugged them into 4 slots, everything worked fine. So all I can say is that the cards SEE NVMe devices but didn't work on my systems.