I have an older motherboard, an ASUS P87ZZ-Pro with Thunderbolt. I recently purchased a VanTec M.2 NVMe + M.2 SATA SSD PCIe X4 Adapter PCI-E NVME adapter card and installed a Samsung 960 PRO 512GB NVME into the adapter.
Windows 10 boots normally, not from the NVME. However, it detects the 960 PRO as being 250GB instead of 512GB. The performance of the drive is quite good.
Why would it be only showing half the actual size of the NVMe?