Dell Precision 3431 Small Form Factor Upgrade Guide

Lifecycle and support

No longer sold new. The manufacturer hasn't published an end-of-support date.

Dates not listed haven't been published by the manufacturer or a reliable third party.

RAM: 4 DDR4 slots, 64 GB ceiling

The motherboard has four 288-pin DDR4 desktop DIMM slots (DIMM1-DIMM4). These are full-size UDIMMs, not the small SO-DIMMs used in laptops, and they are all user-accessible - there is no soldered memory despite one stray line in the service manual suggesting otherwise. That line is erroneous boilerplate and you can ignore it.

Buying tips

• Buy DDR4-2666 UDIMM modules of 16 GB or less - 16 GB per module is the validated maximum
• Get unbuffered (UDIMM) memory only; registered server memory (RDIMM/LRDIMM) will not work
• If you have a Pentium or Core i3, 2666 MT/s modules will simply run at 2400 MT/s

How much RAM can it take?

64 GB in total, using four 16 GB modules. Dell validates 4/8/16 GB modules and does not validate 32 GB UDIMMs on this machine, so 32 GB sticks are a gamble - the 9th generation platform they sit on is not known for reliable 32 GB UDIMM support. If you need more than 32 GB, the safe route is four 16 GB sticks.

Buying tips

• Matched kits of four identical modules are the smoothest option
• 16 GB modules are the sweet spot for price per GB here

ECC or non-ECC?

Both types physically fit, but ECC memory only functions with a Xeon E processor. With a Core i3/i5/i7 or Pentium installed, buy plain non-ECC DDR4 - ECC modules may not even POST on some boards. Dell also pairs ECC with its Reliable Memory features as a Xeon benefit, so don't pay for ECC unless your machine has a Xeon E.

Buying tips

• Check which CPU is installed before ordering ECC memory
• Non-ECC is the safe, compatible choice for Core and Pentium systems

Storage: one M.2 NVMe slot and a flexible SATA bay

There are three storage-related positions. The main one is a single M.2 2280 slot (22 x 80 mm) on the system board for an NVMe SSD. It runs at PCIe Gen3 x4, roughly 32 Gbps. Watch out for Dell's wording: where the spec sheet says "PCIe 40/50", it means Class 40 and Class 50 performance-tier drives, not PCIe Gen 4. Gen4 drives will work but run at Gen3 speed.

Buying tips

• Any M.2 2280 NVMe SSD fits; Gen3 drives are the natural match
• A thermal pad is needed for 512 GB and larger PCIe SSDs
• Dell's Setup Guide lists 1 TB as the M.2 maximum while the spec sheet lists 2 TB

The SATA bay: one 3.5 inch drive or two 2.5 inch drives

The internal drive bay takes either a single 3.5 inch SATA hard drive (up to 8 TB according to the spec sheet, 4 TB according to the Setup Guide) or two 2.5 inch SATA drives stacked together. The 2.5 inch drives must be no more than 9.5 mm thick. With two 2.5 inch SATA drives you can set up RAID 0 or RAID 1 through the Intel Rapid Storage controller - Dell recommends using identical drive models, since mixed drives run at the slower drive's speed.

Buying tips

• Measure twice if you want a big hard drive - Dell's two documents disagree on the top capacity (4 TB vs 8 TB)
• For RAID, buy two identical 2.5 inch SSDs or HDDs
• 2.5 inch drives must be 9.5 mm thick or less

Slots that are not for general SSDs

There is also an M.2 2230 slot, but it is provisioned for a 32 GB Intel Optane memory module rather than a normal SSD, and the slimline optical bay at the front can hold a slim optical drive (some configurations use it for a smart-card reader instead). If you want a second NVMe drive, the way to add one is a PCIe add-in card in one of the expansion slots - Dell's Ultra-Speed Drive card is the example it documents. Expansion slots are half-height.

Buying tips

• Don't buy a 2230 SSD expecting it to work in the Optane slot
• Budget for a half-height NVMe add-in card if you need a second NVMe drive

CPU: socketed LGA1151, 8th/9th Gen Intel

The processor sits in a standard LGA1151 socket on the Intel 300-series chipset, so it is fully replaceable. Supported families are 8th Gen and 9th Gen Intel Core and Pentium (Coffee Lake and Coffee Lake Refresh) plus Xeon E-2100/E-2200 processors. Examples from Dell's lists include the Pentium Gold G5420, Core i3-9100/9300, i5-9500/9600, i7-9700, i9-9900, Core i7-8700, and Xeon E-2174G, E-2224/E-2224G, E-2236 and E-2246G. Dell's documents don't all agree: the service manual list omits the Xeon E-2246G and the Core i3-9100 that the spec sheet includes.

Buying tips

• Check Dell's CPU support list for your exact BIOS version before buying
• A BIOS update may be needed before an 8th/9th Gen swap - update first, with the old CPU still installed
• Keep the original processor until the new one is confirmed working

How fast a CPU can the small chassis cool?

The validated maximum is a 95 W processor - the i5-9600, i7-9700, i9-9900 and Xeon E-2236-class parts sit at that level, with most others at around 65 W. Bear in mind the small form factor cooling limits sustained boost, so a 95 W chip won't always behave like the same CPU in a tower. If you want ECC memory support, you need to install a Xeon E processor.

Buying tips

• 95 W is the ceiling - don't expect more from an unlisted processor
• Match the CPU choice to your RAM: Xeon E for ECC, Core/Pentium for non-ECC

How to upgrade

Before you start

• Back up anything you can't afford to lose - especially before storage or BIOS work
• Shut down the machine, switch off the PSU if it has a switch, and unplug the power cable and peripherals
• Ground yourself (touch the metal chassis or use an anti-static strap) and work on a hard, uncluttered surface
• Open the case following the owner's manual for your exact chassis - remove the side panel as described there rather than guessing at latches or screws
• Install the part firmly and evenly: memory clicks down on both ends, M.2 cards seat at an angle and are secured with the screw described in the manual, CPUs drop into the keyed socket without force
• Close the case, reconnect power, and switch on
• Check that the BIOS/UEFI sees the new part and reports the expected capacity or model; update the BIOS/firmware if the part isn't recognised
• If anything isn't detected, reseat the part and re-check before assuming it's incompatible

Steps

1. RAM or CPU
   Follow the outline above. For the CPU, note that an 8th/9th Gen upgrade may require a BIOS update applied first with your existing processor, and that Dell's CPU support list is the authority on what your BIOS version accepts. The exact removal of the cooler and socket cover is described in the owner's manual.
2. M.2 SSD
   Follow the outline above. Use the M.2 2280 slot on the system board, fit the thermal pad required for 512 GB and larger PCIe SSDs, and secure the card as the owner's manual shows. A second NVMe drive needs a PCIe add-in card.
3. SATA drives
   Follow the outline above. The bay accepts one 3.5 inch drive or two 2.5 inch drives up to 9.5 mm thick. If you want RAID 0/1, use two identical 2.5 inch SATA drives and set up the array in the Intel Rapid Storage utility; RAID is not available when the Optane module is in use.

Good to know

• Where Dell's own documents differ - M.2 maximum (1 TB vs 2 TB) and 3.5 inch maximum (4 TB vs 8 TB) - treat the larger figure as likely but unconfirmed, and check the drive physically fits before buying.
• We may earn a commission when you buy through links on this page. Prices update live elsewhere on the page.

Frequently asked questions

How much RAM can the Dell Precision 3431 SFF take?

64 GB, using four 16 GB DDR4 UDIMMs - 16 GB per module is the validated maximum. Dell does not validate 32 GB modules on this machine.

Is the memory soldered?

No. All four DDR4 slots are socketed and user-replaceable. One line in the service manual claims the memory is embedded on the board; it is erroneous boilerplate and contradicts the same manual's board layout.

Does it support ECC memory?

Only with a Xeon E processor. With a Core or Pentium CPU, buy non-ECC DDR4. Either type fits physically, but ECC won't be enabled without a Xeon E.

Does it support NVMe and PCIe Gen4 SSDs?

It has one M.2 2280 NVMe slot running at PCIe Gen3 x4 (about 32 Gbps). Gen4 drives work but run at Gen3 speed. Dell's "PCIe 40/50" wording refers to Class 40/50 drives, not PCIe generations.

How many drives can I install?

One M.2 2280 SSD plus either one 3.5 inch drive or two 2.5 inch drives in the internal bay. The M.2 2230 slot is reserved for a 32 GB Optane module, not a regular SSD. Another NVMe drive requires a PCIe add-in card.

Can I upgrade the CPU to an i9-9900 or a Xeon?

Yes - the socket is LGA1151 and the machine accepts 8th/9th Gen Core, Pentium and Xeon E-2100/E-2200 processors up to 95 W. Update the BIOS first if needed, and check Dell's CPU support list, since Dell's documents don't agree on every supported model.

Official documents and references

• PDF Dell Precision 3431 Workstation Service/Owner's Manual (PDF)
  Disassembly and board layout
• PDF Dell Precision 3431 official specification sheet (PDF)
  Full supported options list
• Dell Setup and Specifications - Memory
  Memory types, speeds and capacities
• Dell Setup and Specifications - Storage
  Drive bays, interfaces and RAID support