Dell Latitude 5591 Upgrade Guide

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

What fits. The Latitude 5591 has two user-accessible 260-pin DDR4 SO-DIMM slots and no soldered memory, so both sticks are yours to replace. The memory is DDR4, non-ECC and unbuffered, running at DDR4-2666 (PC4-21300). ECC or registered server modules are not supported.

The limits. The ceiling is a hard 32 GB: two 16 GB modules. A single 32 GB SO-DIMM will not even POST in this machine, so 64 GB is not possible - a user who tried it reported exactly that outcome, and Dell and Crucial both cap the model at 32 GB. Don't let anyone sell you '64 GB upgrade kits' for it. Note that a 32-bit operating system will only show a fraction of your memory; run 64-bit Windows or Ubuntu to use it all.

What to watch out for. DDR4-3200 modules physically fit and work, but the machine clocks them down to 2666 MT/s, so there's no benefit in paying extra for them. Owners report that 1Rx8 and 2Rx8 PC4-3200 sticks pulled from other Latitudes work fine and can be mixed to reach 32 GB. Dell's own guidance is to use matched pairs (same size, speed and technology); mismatched sticks still run, with a small performance penalty. One confusing thing you may find: a generic page in Dell's service manual claims the DDR4 memory is soldered and not replaceable. That's boilerplate text meant for other models - the 5591-specific documentation and the machine itself both show two removable SO-DIMM slots.

Buying tips. Look for DDR4-2666 (PC4-21300) SO-DIMM kits, 2x 8 GB or 2x 16 GB, non-ECC. Faster-rated DDR4-3200 is fine as a substitute if it's cheaper. Skip 32 GB modules entirely.

Buying tips

• Matched pair: 2x 8 GB or 2x 16 GB DDR4-2666 non-ECC SO-DIMM
• DDR4-3200 works but runs at 2666 MT/s - buy whichever is better value
• Avoid 32 GB modules (no POST), ECC or registered memory, and any 64 GB claims

Storage

What fits. You have three drive positions to work with. The primary slot is an M.2 2280 that accepts either a SATA AHCI drive or an NVMe drive over PCIe 3.0 x4. There is also a 2.5-inch SATA bay for an HDD or SSD, and the M.2 2230 WWAN slot can take a small SSD as a third drive. Drive heights in the 2.5-inch bay are limited to 7 mm.

The limits. Dell lists capacities up to 1 TB on the primary slot (PCIe/NVMe) or 512 GB (SATA) and up to 1 TB in the 2.5-inch bay, but treat these as configuration maxima rather than verified hard limits - they are the largest drives Dell sold, not a proven ceiling. For the WWAN slot, Dell lists an M.2 2230 SSD up to 256 GB on a PCIe 3.0 x2 link, and you need a 2230-to-2242 adapter board to make it fit. The platform is PCIe 3.0 throughout, so a Gen 4 or Gen 5 NVMe drive will run at Gen 3 speed - don't pay a premium for one.

What to watch out for. The biggest gotcha is the second drive. Dell only supplies the 2.5-inch caddy and cable as part of a dual-drive configuration bought from the factory; the bracket and harness are not sold separately afterwards. If you want an SSD plus a second drive, either buy a unit that was configured with two drives, or source third-party brackets and cables. Also note the primary M.2 slot is a combo slot: SATA and NVMe drives both fit, but the drive runs on whichever interface it supports. Self-encrypting (OPAL) drives are supported on the primary and 2.5-inch options.

Buying tips. For a single big upgrade, a 1 TB M.2 2280 NVMe SSD in the primary slot is the simplest path. Check whether your machine already has the second-drive hardware before buying a 2.5-inch SSD. The WWAN-slot SSD trick works but is fiddly and capped at a small capacity, so keep it as a backup plan.

Buying tips

• M.2 2280 NVMe SSD (PCIe 3.0) for the primary slot - simplest upgrade
• 2.5-inch drives must be 7 mm thick, and you need the Dell caddy/cable
• Gen 4/5 SSDs add nothing here; the slot is PCIe 3.0

CPU

What fits. This is the reason enthusiasts seek out the 5591: the processor sits in a socket and can be replaced. The physical socket is Intel's mobile PGA socket (rPGA946B, sometimes called Socket G2), carrying 8th-generation Coffee Lake-H mobile chips. Dell's documentation doesn't spell out the socket type, so ignore anything that describes it as a desktop LGA1151 part - you need a mobile PGA chip, and a desktop processor will not fit. All supported parts use the integrated Intel UHD 630 graphics; the 5591 has no discrete GPU option.

The limits. Dell validates three processors: Core i5-8300H (4 cores/8 threads, 2.3 GHz), Core i5-8400H (4 cores/8 threads, 2.5 GHz, vPro) and Core i7-8850H (6 cores/12 threads, 2.6 GHz, vPro). All are 35 W cTDP parts - the Coffee Lake-H silicon is rated 45 W but is configured down to 35 W in this chassis. The i7-8850H is the top validated chip and the only one of the three with six cores.

What to watch out for. Other Coffee Lake-H PGA processors (the 45 W parts, for example) are not guaranteed to work: the BIOS and the cooling solution were tuned for the three SKUs above, and Dell offers no validation for anything else. If you gamble on an unlisted chip, it may not boot or may overheat. Also manage expectations - going from an i5-8300H to an i7-8850H adds cores, but it's the same generation and the same integrated graphics, so it's a modest step, not a transformation.

Buying tips. Buy only a used or new mobile PGA Coffee Lake-H chip on Dell's validated list. Before ordering, check that your BIOS is up to date and confirm your current processor in the BIOS or system info screen. Factor in thermal paste and careful handling; if you're not comfortable working on a laptop motherboard, a repair shop can swap the chip cheaply.

Buying tips

• Validated upgrades: i5-8300H, i5-8400H, i7-8850H - all 35 W cTDP
• Mobile PGA (rPGA946B) chips only - never a desktop CPU
• Stay on Dell's list; unvalidated 45 W parts are a gamble

How to upgrade

Before you start

• Back up your data before touching anything.
• Shut the laptop down fully and unplug the AC adapter.
• Ground yourself to avoid static damage to the components.
• Open the case and fit the part, working gently and keeping screws sorted.
• Close the case, reconnect power and boot.
• Check in the BIOS (and then the operating system) that the new RAM, drive or CPU is detected at the right capacity and speed.

Steps

1. Opening the case safely
   The exact disassembly - which screws to remove, how the base cover releases, where the drive brackets and CPU socket latch are - is model-specific, so follow the illustrated procedures in the Dell Latitude 15 5591 Service Manual rather than guessing. Take the battery and static precautions seriously; a dropped screw or a levered connector is the most common way an upgrade turns into a repair.

Good to know

• Don't confuse the Latitude 5591 with the Latitude 5590 - the 5590 has a soldered CPU and takes none of these upgrades.
• The RAM ceiling is hard at 32 GB (2x 16 GB). 32 GB single modules are a dead end.
• Buy the dual-drive configuration up front if you want an M.2 SSD plus a 2.5-inch drive; the second-drive hardware isn't sold separately.
• Configurations vary by region, so the exact CPU and storage combinations sold differ between markets.
• Third-party sellers sometimes advertise DDR4-3200 and Gen 4/5 NVMe support. The platform is DDR4-2666 and PCIe 3.0; faster parts run at reduced speed.

Frequently asked questions

How much RAM can the Dell Latitude 5591 take?

32 GB maximum, in two 16 GB DDR4 SO-DIMMs. Both slots are user-accessible and nothing is soldered.

Can the Latitude 5591 run 64 GB of RAM?

No. A 32 GB single SO-DIMM will not even POST in this model, so there is no way to reach 64 GB. Dell and Crucial both cap it at 32 GB, even though the i7-8850H CPU itself supports more.

Does it support DDR4-3200 memory?

The platform is DDR4-2666. DDR4-3200 modules physically work but are clocked down to 2666 MT/s. Claims of 3200 MT/s or faster support come from third-party sellers and don't change the machine's limits.

Can I upgrade the CPU in the Latitude 5591?

Yes - it's one of the few Latitudes with a socketed processor (mobile PGA rPGA946B). Dell validates the i5-8300H, i5-8400H and i7-8850H, all 35 W parts. Other Coffee Lake-H chips are unvalidated and may not work with the BIOS or cooling. Never buy a desktop LGA1151 CPU for it.

Can I add a second SSD or hard drive?

You can, but only if the 2.5-inch caddy and cable are present. Dell supplies that hardware only with dual-drive configurations bought from the factory and doesn't sell it separately afterwards, so buy a dual-drive unit or find third-party brackets. The M.2 2280 slot itself accepts both SATA and NVMe drives.

Does the Latitude 5591 support PCIe Gen 4 or Gen 5 SSDs?

No. Its slots are PCIe 3.0. A Gen 4 or Gen 5 drive will fit and run at Gen 3 speed, so you pay more for no benefit. Third-party listings claiming Gen 4/5 support are mistaken.

Can I use the WWAN slot for a third drive?

Yes, with caveats. The M.2 2230 WWAN slot can hold a small SSD (Dell lists up to 256 GB) on a PCIe 3.0 x2 link, but you need a 2230-to-2242 adapter board, and you lose the option of a mobile broadband card.

Official documents and references

• PDF Dell Latitude 5591 Setup and Specifications Guide (PDF)
  Official - full memory, storage and CPU specifications
• Dell Latitude 5591 Setup & Specifications: Memory
  Official - slot count, module types and capacities
• PDF Dell Latitude 15 5591 Service Manual (PDF)
  Illustrated disassembly, component removal and replacement procedures
• Dell Latitude Memory Compatibility Guide
  Official - module matching and OS memory limits
• Dell community: Latitude 5591 - is 64 GB RAM possible?
  User test showing 32 GB modules do not POST
• Dell community: Latitude 5591 memory compatibility question
  User reports on mixed DDR4-3200 modules working at 2666 MT/s