The Precision 5820 Tower is Dell's second-most powerful desktop workstationAfA¢A¢aEUR^1A¬A¢a,¬A which, judging by the ,567 test model we received, is akin to saying the Boeing 747-8 is only the second-biggest airliner in the world. It's an evolution of the Precision 5810 Tower, which we reviewed to high praise back in 2015. On paper, the Precision 5820 is a better value and a total beast for pro applications that can take advantage of its specialized memory, pro-grade Quadro/Radeon Pro graphics, ISV certifications, and Xeon horsepower.
The motherboard offers plenty of room for expandability. You get two PCI Express (PCIe) x16 slots in full x16 bandwidth for graphics cards, one PCIe x16 wired internally as an x8 slot, another wired as x4, and one final PCIe x16, wired for x1. There's even a single old-school PCI slot. You can install PCIe cards without screws or tools; a clip holds down a retainer bar that keeps cards in place.
For storage, the motherboard has eight SATA ports, plus one extra that's allocated to an optical drive. If you want an M.2 slot for high-speed SSDs, however, you'll need to opt for one or more of Dell's PCIe Ultra-Speed cards.
The review unit I have in hand has the Dell Ultra-Speed Duo card, which has two M.2 Type-2280 slots on it, one of which is occupied by a 512GB PCIe drive with NVMe support. On our unofficial Crystal DiskMark benchmark testing (using a 50MiB cluster size), the drive delivered 2,188MBps read and 1,363MBps write speeds. Those aren't record-breaking numbers, but that doesn't detract from the fact that it's very fast storage. (A Dell Ultra-Speed Quad card, with four M.2 slots, is also an option.)