Dell Precision 5820 Tower Upgrade Guide: RAM, Storage, CPU

Updated Oct. 8, 2026 · Written from this device's verified specifications

This guide covers adding memory, bigger or faster storage, and what to know before changing the processor in a Dell Precision 5820 Tower (also sold as the Precision T5820). The short answer: it takes up to 512 GB of DDR4 in eight slots, SATA/SAS drives in front bays, NVMe through an add-in card or a PCIe-enabled FlexBay, and what you can use depends heavily on whether your CPU is a Xeon W or a Core X.

At a glance

  • 8 DDR4 DIMM slots, four-channel, up to 512 GB total at up to 2933 MT/s (depends on the CPU)
  • ECC RDIMM works only with Xeon W CPUs; non-ECC UDIMM works only with Core X CPUs and tops out at 256 GB
  • No on-board M.2 slot: NVMe needs a Dell Quad M.2 card or a FlexBay with a PCIe backplane
  • Single-socket CPU, Xeon W-21xx/22xx or Core X, up to 165 W; Dell's documents don't name the socket
  • All PCIe slots are Gen 3
DDR4 DIMM slots (4-channel)8 × DDR4 DIMM · up to 512 GB total · 2933 MT/s
Front FlexBay 2.5"/3.5" SATA/SAS drive bays4 × HDD / SSD 3.5" / 2.5" (SATA / SAS)
NVMe via Quad M.2 card or PCIe FlexBay4 × SSD M.2 2280 / U.2 (NVMe)
8 × DIMM · DDR4up to 512 GB totalFront FlexBay 2.5"/3.5" SATA/SAS drive bays4 × HDD / SSD 3.5" / 2.5" (SATA / SAS)NVMe via Quad M.2 card or PCIe FlexBay4 × SSD M.2 2280 / U.2 (NVMe)
Schematic of the upgradeable slots (not to scale). Check the owner's manual for their exact positions.

RAM: DDR4 DIMMs, up to 512 GB

The Precision 5820 has 8 full-size DDR4 DIMM slots arranged in four channels. No SO-DIMM or soldered memory is mentioned in Dell's documents, so memory appears to live entirely in the DIMM slots. The minimum configuration is 8 GB (1 x 8 GB).

Which type you can use depends on your CPU. ECC registered DIMMs (RDIMM) work only with Xeon W processors. Non-ECC unbuffered DIMMs (UDIMM) work only with Core X processors and are limited to 256 GB in total.

The total ceiling and speed also depend on the CPU generation. Skylake CPUs allow 256 GB at 2666 MT/s. Cascade Lake CPUs allow 512 GB at 2933 MT/s. Dell's manual lists modules of 32 GB at 2666 MT/s and 64 GB at 2933 MT/s, and notes that 3200 MT/s RDIMMs run at 2933 MT/s on Cascade Lake. If you fit 2933 MT/s RDIMMs to a Skylake Xeon W, they run at 2666 MT/s.

Dell's documents disagree here. The spec sheet reads as 512 GB at 2666 and 256 GB at 2933, while the manual gives 256 GB total at 2666 and 512 GB total at 2933. The manual's per-slot figures are more detailed and later, so we'd go with those.

Buying tips

  • Check whether your CPU is a Xeon W or a Core X first: it decides RDIMM (ECC) versus UDIMM (non-ECC).
  • Match the memory speed to your CPU generation; faster modules in a Skylake system just run at 2666 MT/s.
  • Buy matched modules and fill the four channels evenly where you can.
  • 2666 MT/s memory was discontinued by Dell on configurations bought after October 2020, so newer systems may have faster kits.

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Storage: SATA/SAS bays and NVMe options

Front drive bays: two front FlexBays each hold up to two 2.5-inch or 3.5-inch drives, so you get up to four SATA drives without any extras. An optional 5.25-inch bay (factory option or customer kit) adds up to two 2.5-inch drives or one 3.5-inch drive. Dell's documents don't state drive thickness limits, so check the owner's manual if you plan to use unusual drives. SAS drives, optional RAID controllers and self-encrypting drives (SED) work only on Xeon W systems.

NVMe: there is no on-board M.2 slot. You can add NVMe SSDs with a Dell Ultra-Speed Drive Quad x16 card (up to four M.2 drives), or in a FlexBay fitted with a PCIe backplane (M.2 or U.2). If your system wasn't ordered with NVMe FlexBay support, Dell's kit 750-ABDF converts FlexBay 1 to PCIe. All PCIe slots are Gen 3, so drives will run at Gen 3 speeds.

Core X limits: with Core X CPUs, only one front M.2 NVMe drive is supported because there are fewer PCIe lanes. U.2 Optane is available only with Xeon W Cascade Lake.

What's unconfirmed: Dell's documents don't state the M.2 lengths supported, so 2280 is the likely size but not confirmed. For the Quad card, the spec sheet says 4 x 2 TB and the manual says 4 x 1 TB. Larger drives probably work, but that isn't confirmed.

Buying tips

  • Look inside or check your service tag to see whether you already have a PCIe-enabled FlexBay before buying NVMe drives.
  • If you don't have one, choose between the Quad M.2 card and the 750-ABDF conversion kit.
  • Core X owners should plan for a single front M.2 drive only.
  • For ordinary 2.5-inch SATA SSDs, no extra hardware is needed; they go straight into a FlexBay.
  • Don't buy SAS drives or a RAID controller unless you have a Xeon W CPU.

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How to upgrade

Before you start

  • Find your service tag and check your exact configuration with Dell, since details vary by build.
  • Identify whether your CPU is a Xeon W or a Core X, and Skylake or Cascade Lake, as this decides compatible memory and NVMe options.
  • Back up your important files.
  • Have the owner's manual open for exact disassembly steps.
  • Check the power supply rating (425 W or 950 W) if you plan to add high-power parts.

Steps

  1. Back up your data
    Copy important files to an external drive or cloud storage before opening the machine, especially if you are changing or cloning storage.
  2. Power off and unplug
    Shut the system down fully, unplug the power cable and any peripherals, then press the power button once to discharge residual power.
  3. Ground yourself
    Touch bare metal on the chassis or use an anti-static wrist strap, and handle parts by their edges.
  4. Open the case
    Remove the side cover following the owner's manual. Lay the tower on its side on a stable, clean surface if the manual suggests it.
  5. Install the part
    For memory, fit DIMMs into the slots as the manual's memory guide describes. For SATA drives, use the FlexBay carriers. For NVMe, fit the Quad M.2 card in a PCIe slot or use a PCIe-enabled FlexBay (kit 750-ABDF converts FlexBay 1 if needed). Follow the manual for exact procedures.
  6. Close up and reconnect
    Refit the cover, reconnect the cables and power on.
  7. Check it is detected
    Enter the BIOS setup at startup (or check the system information screen) to confirm the new memory or drive is recognized, then check in your operating system. New drives will need to be initialized and formatted.

Good to know

  • Dell's documents don't name the CPU socket. Both Xeon W and Core X chips here are likely LGA 2066, but that is unconfirmed, so check compatibility with Dell before buying a processor.
  • Xeon W and Core X are different platforms (Intel C422 vs X299 chipsets). ECC RDIMM, SAS and SED work only with Xeon W; Core X uses non-ECC UDIMM only.
  • Dell's spec sheet and manual disagree on the memory speed and capacity pairing, and on the Quad M.2 card's per-drive capacity (2 TB vs 1 TB). We follow the manual for memory; the Quad card capacity is unconfirmed.
  • M.2 lengths and drive thickness limits aren't stated in Dell's documents.
  • The power supply is 425 W or 950 W depending on configuration, which matters for 165 W CPUs and power-hungry graphics cards.
  • Core X systems ship with Windows 10 Pro, and listed Linux support covers RHEL 8, Ubuntu 18.04 and SLES 12 SP2.
  • Spec details vary by configuration, so verify your exact build with your service tag before buying parts.

Frequently asked questions

How much RAM can the Dell Precision 5820 Tower take?

Up to 512 GB across 8 DDR4 slots with a Cascade Lake Xeon W using 64 GB RDIMMs. Skylake CPUs allow 256 GB, and non-ECC UDIMM systems (Core X) are limited to 256 GB.

Does the Precision 5820 support ECC memory?

Yes, but only with Xeon W CPUs, which use ECC registered DIMMs (RDIMM). Core X systems use non-ECC UDIMMs only.

Does the Precision 5820 have an M.2 slot?

No, there is no on-board M.2 slot. You can add M.2 NVMe drives with a Dell Ultra-Speed Drive Quad x16 card or a FlexBay with a PCIe backplane.

Can I put an NVMe SSD in the front bays?

Only in a FlexBay with a PCIe backplane. If yours doesn't have one, Dell's kit 750-ABDF converts FlexBay 1. Core X systems support only one front M.2 drive.

Can I upgrade the CPU in a Precision 5820?

The system is single-socket and supports Xeon W-21xx/22xx and Core X processors up to 165 W. Dell's documents don't name the socket, though these CPUs are likely LGA 2066 (unconfirmed). Xeon W and Core X use different chipsets, so check your platform and your power supply before choosing a CPU.

How many SATA drives can it hold?

Up to four 2.5-inch or 3.5-inch drives in the two front FlexBays. With the optional 5.25-inch bay, up to six 2.5-inch or five 3.5-inch drives.

Official documents and references

This guide was written with AI assistance from the compatibility data PartsPrices verified against the manufacturer's documents. Always check your exact model and the owner's manual before buying or opening your computer.