Dell OptiPlex 7040 SFF Upgrade Guide: RAM, SSD and CPU

Lifecycle and support

A current model: sold new and supported.

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

RAM: four DDR4 slots, check the 64 GB ceiling

The 7040 SFF has four full-size DDR4 UDIMM slots (desktop-size, not laptop SO-DIMMs). Each slot takes up to 16 GB, and Dell lists 4, 8 and 16 GB module sizes. Memory runs at 2133 MT/s, and faster modules will simply run at that speed. Dell's brochure describes the memory as dual-channel.

Use unbuffered, non-ECC modules. Dell's manual gives a 64 GB maximum (4 x 16 GB), but Dell's brochure and fact sheet say up to 32 GB. The manual's arithmetic adds up, but we found nothing confirming 64 GB working in practice, so be cautious before buying four 16 GB modules.

Dell's documents also cover the Micro model, which has only two memory slots and a lower maximum. Make sure any spec you rely on is for the Small Form Factor.

Buying tips

• Buy DDR4 unbuffered non-ECC UDIMMs, not SO-DIMMs and not registered or ECC modules.
• DDR4-2133 is enough. Faster modules work but will run at 2133.
• If you want more than 32 GB, treat 64 GB as unconfirmed and consider starting with 2 x 16 GB.
• Buying matched modules is a sensible choice, given the dual-channel design.

Storage: one M.2 slot plus SATA bays

The board has one M.2 slot for 22 x 80 mm (2280) drives. It is documented as supporting both M.2 SATA and PCIe 3.0 x4 NVMe SSDs. Shorter lengths such as 2242 or 2260 are not confirmed, so stick with 2280. If you want to boot from an NVMe drive, check that your BIOS supports NVMe booting.

There is also one internal 3.5-inch SATA bay, which can be converted to hold two 2.5-inch drives. These two 2.5-inch positions replace the 3.5-inch bay and are not extra bays, and you will likely need a bracket or caddy. Dell's documents don't state a 2.5-inch thickness limit (7 mm or 9.5 mm), so check your drive's height against the bay in the owner's manual.

The system has three SATA ports (1.5, 3 and 6 Gbps) shared with the optical drive. Dell's brochure lists hard drives up to 2 TB, but that is just the largest factory option and not a stated limit. Dell's documents also disagree on the optical bay: the manual's table mentions 5.25-inch bays, while the brochure describes one slim optical bay, which fits the SFF case better.

Buying tips

• For the biggest speed boost, a 2280 NVMe SSD in the M.2 slot is the best fit. A 2280 M.2 SATA drive also works.
• Don't buy 2242 or 2260 M.2 drives, as those lengths are unconfirmed.
• For a SATA SSD, get a 2.5-inch drive and a bracket or adapter for the 3.5-inch bay.
• Don't treat 2 TB as a ceiling for SATA drives, but it is the largest size Dell offered.

CPU: 6th-gen Core, 65 W maximum

Dell lists 6th-generation (Skylake) Intel Core i3, i5 and i7 processors for this system, with a 65 W maximum and up to 8 MB cache. The chipset is Intel Q170. The i3 models are dual-core and the i5 and i7 models are quad-core, so moving from an i3 to a quad-core i5 or i7 is the realistic upgrade.

Dell's documents don't name the socket. Chips for this platform use LGA1151, so the processor is likely replaceable, but confirm in Dell's service manual before buying. Dell doesn't say whether 7th-generation CPUs are supported, so don't assume they work.

The standard power supply is 180 W, which limits how far you can go with the CPU, so stay at or under 65 W.

Buying tips

• Look for 65 W or lower 6th-gen Core i5 or i7 chips. Avoid higher-wattage models.
• Don't buy a 7th-gen CPU unless you have found confirmation that this system supports it.
• Confirm the socket in the service manual before ordering.
• A boxed cooler isn't a given for the compact case, so check the heatsink in your machine before you swap anything.

How to upgrade

Before you start

• Confirm you have the Small Form Factor model, not the Micro or Mini Tower, as they share documents but differ in specs.
• Back up your files before opening the case, especially if you are replacing or cloning a drive.
• Have the owner's manual (and the service manual for a CPU swap) open for exact disassembly steps.
• Check that your BIOS is recent enough for the part you are adding, particularly for NVMe booting.
• Gather a small screwdriver and, for 2.5-inch drives, a bracket or caddy.

Steps

1. Back up and prepare
   Back up your data and note your Windows licence or recovery details. If you are replacing the system drive, have installation media or a cloning tool ready.
2. Power off and unplug
   Shut the computer down fully, unplug the power cable and any other cables, and hold the power button for a few seconds to drain residual power.
3. Ground yourself
   Work on a clean, hard surface. Touch bare metal on the case before handling parts, and hold components by their edges.
4. Open the case
   Remove the cover following the owner's manual for the Small Form Factor. It shows exactly how to release the cover and reach the memory, drive bays and M.2 slot.
5. Install the new part
   For RAM, fit the DDR4 modules into the slots as the manual describes. For an SSD, place it in the M.2 slot or the 3.5-inch bay (with a bracket for 2.5-inch drives). For a CPU, follow the service manual, and confirm the socket first.
6. Close the case and reconnect
   Refit the cover, reconnect your cables and power on.
7. Check that the BIOS sees the part
   Press the BIOS setup key at startup and confirm the new memory total, drive or processor is listed. For a new NVMe drive, check that the system can boot from it before installing your operating system.

Good to know

• The 64 GB RAM maximum comes from Dell's manual. Dell's brochure says 32 GB, and 64 GB isn't confirmed in practice.
• Dell's documents don't name the CPU socket. LGA1151 is inferred from the Q170 chipset, so verify it in the service manual.
• 7th-gen CPU support is not confirmed. Dell lists only 6th-gen Core i3, i5 and i7 at up to 65 W.
• M.2 lengths shorter than 2280 and 2.5-inch drive thickness limits are not documented.
• Dell's manual and brochure disagree on the optical and 5.25-inch bays, and we couldn't verify which is correct for the SFF.
• The case takes half-height expansion cards only (one PCIe x16 Gen 3 and one PCIe x4), and the 180 W power supply limits graphics card and CPU upgrades.

Frequently asked questions

How much RAM can the Dell OptiPlex 7040 SFF take?

Dell's owner's manual says 64 GB (four slots of 16 GB each). Dell's brochure and fact sheet say up to 32 GB, and we found nothing confirming 64 GB in practice. 32 GB is the safer target.

What type of RAM does the OptiPlex 7040 SFF use?

Full-size DDR4 UDIMMs, unbuffered and non-ECC, running at 2133 MT/s. Faster modules work but run at 2133. Laptop SO-DIMMs won't fit.

Does the OptiPlex 7040 SFF support NVMe SSDs?

Yes. The M.2 slot is documented for 2280 drives, either SATA or PCIe 3.0 x4 NVMe. If you want to boot from NVMe, check that your BIOS supports it.

Can I add a 2.5-inch SSD or a second drive?

Yes. The 3.5-inch bay can be converted to hold two 2.5-inch SATA drives, and you will likely need a bracket or caddy. Dell's documents don't state a thickness limit, so check the fit.

Can I upgrade the CPU in the OptiPlex 7040 SFF?

Probably. Dell's documents don't name the socket, but chips for this platform use LGA1151. Dell lists only 6th-gen Core i3, i5 and i7 up to 65 W. Confirm the socket in the service manual first.

Does the OptiPlex 7040 SFF support 7th-gen Intel CPUs?

Dell's documents don't say. Only 6th-generation processors are listed, so don't assume 7th-gen chips will work.

Official documents and references

• Dell OptiPlex 7040 SFF Owner's Manual: Specifications
  Official memory, drive and processor specifications
• Dell OptiPlex 7040 Small Form Factor Owner's Manual
  Official disassembly and component replacement guidance
• PDF OptiPlex 7040 specifications brochure (PDF)
  Memory, drive options and 65 W processor listing
• PDF Dell OptiPlex fact sheet (PDF)
  M.2 slot and memory overview
• Dell OptiPlex 7040 SFF at Hardware Corner
  Third-party summary of M.2, SATA and expansion slots