HP EliteDesk 800 G4 Tower upgrade guide: RAM, SSD and CPU

Updated Oct. 19, 2026 · Written from this device's verified specifications

The HP EliteDesk 800 G4 Tower (also sold as 800 G4 MT) is one of the friendlier business desktops to upgrade: all four memory slots are user-accessible with nothing soldered down, there are two M.2 slots for NVMe SSDs plus three SATA drive bays, and the processor sits in a socket rather than being soldered to the board. This guide covers what fits in each area and what to watch out for before you buy. One warning up front: the G4 family includes several very different machines — the Tower (this one), the SFF, the Desktop Mini and the near-identical 880 G4 Tower. The Mini uses laptop-style SO-DIMMs and the SFF needs low-profile cards, so make sure you have the Tower chassis before ordering parts. Also, if you run 32-bit Windows you cannot use more than about 3 GB of memory; anything above 4 GB needs a 64-bit operating system.

At a glance

  • RAM: 4 x DDR4 DIMM slots, up to 64 GB total (4 x 16 GB), nothing soldered
  • Storage: 2 x M.2 NVMe slots (2280/2230) plus 3 SATA 6 Gb/s bays
  • CPU: socketed LGA1151v2, 8th-gen Intel only, up to 95 W
4× DDR4 DIMM (non-ECC, 64 GB max)4 × DDR4 DIMM · up to 64 GB total · 2666 MT/s
2× M.2 2280/2230 NVMe (PCIe 3.0 x4)2 × SSD M.2 2230 / M.2 2280 (NVMe)
3× SATA 6 Gb/s bays (2× 3.5", 1× 2.5")3 × HDD / SSD 2.5" / 3.5" (SATA)
LGA1151v2 CPU socket (8th Gen Intel)LGA1151 (8th/9th gen) · Core 8th gen · max 95 W
CPU · LGA1151 v2max 95 W4 × DIMM · DDR4up to 64 GB total2× M.2 2280/2230 NVMe (PCIe 3.0x4)2 × SSD M.2 2230 / M.2 2280 (NVMe)3× SATA 6 Gb/s bays (2× 3.5",1× 2.5")3 × HDD / SSD 2.5" / 3.5" (SATA)
Schematic of the upgradeable slots (not to scale). Check the owner's manual for their exact positions.

Lifecycle and support

Standard support ended on December 2024 (estimate).

2018201920202021202220232024202520262027Today11 · Release · August 201822 · End of sale · January 202033 · EOL · December 202444 · EOSL · December 2024
Filled dots: dates published by the manufacturer. Hollow dots: estimates from third-party sources.
MilestoneDate
Release
First available to buy.		 August 2018 Estimate JP-market announce/first availability; consistent with 2018 release per hardware-corner.net (https://www.hardware-corner.net/desktop-models/HP-EliteDesk-800-G4-Tower/)
Source ↗
End of sale
No longer sold new by the manufacturer (Dell calls this 'End of Life', Lenovo 'Withdrawn').		 January 2020 Estimate JP market (販売終了 2020年1月)
Source ↗
End of life (EOL)
The manufacturer stops developing the product: no new BIOS, firmware or driver releases.		 December 2024 Estimate The source publishes one 保守期限 date that the notes map to both end-of-life and end-of-standard-support
Source ↗
End of standard support (EOSL)
Standard warranty and support contracts can no longer be renewed.		 December 2024 Estimate JP market (保守期限)
Source ↗

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

Memory (RAM)

The Tower has four 288-pin desktop DIMM slots, all customer-accessible, and no memory is soldered to the board. It takes unbuffered, non-ECC DDR4 only, in a dual-channel arrangement, up to 16 GB per module for a maximum of 64 GB (four 16 GB sticks). HP warns that unsupported modules may not work, and the manual states the system does not operate properly with them — so skip ECC or registered/server memory, and skip x4-device modules. x8 and x16 devices are supported, single- or double-sided.

Speed is set by your processor, not by the board. With an 8th-gen Core i5 or i7, memory runs at up to 2666 MT/s; with a Core i3, Pentium or Celeron, it is capped at 2400 MT/s. Note that HP's documents disagree here: the service manual specifies DDR4-2400 CL17 modules, while the spec sheets list DDR4-2666. Both work — faster modules simply run at the slower rate — so buy whichever works out better and don't worry about the discrepancy.

Be careful with capacity claims you may see elsewhere: 32 GB unbuffered modules are not validated for this platform, so 64 GB means four 16 GB sticks, not two 32 GB ones.

Buying tips: match the module type to the manual (DDR4, unbuffered, non-ECC), and if you want the full 2666 MT/s, make sure you have an 8th-gen i5 or i7. If you are filling empty slots alongside existing memory, try to keep the total balanced across the two channels.

Buying tips

  • DDR4 DIMM (desktop size), unbuffered, non-ECC only
  • Max 16 GB per stick, 64 GB total with 4 x 16 GB
  • 2666 MT/s needs an 8th-gen i5/i7; otherwise 2400 MT/s
  • Avoid ECC, registered and x4-device modules

Storage (SSD and hard drive)

Storage is a real strength of this machine. You get two M.2 slots for NVMe SSDs wired as PCIe 3.0 x4, accepting either 2280 or 2230 length drives (a shorter 2230 drive needs the spacer and screw position for that length). There is also a third M.2 2230 slot, but that one is wired as PCIe x1 and is for the Wi-Fi/Bluetooth card only — it cannot take a drive. HP does not document M.2 SATA support in the storage slots on this chassis, so treat the M.2 slots as NVMe-only to be safe.

For SATA drives there are three 6 Gb/s internal bays: two 3.5-inch and one dedicated 2.5-inch. A 2.5-inch drive fits a 3.5-inch bay only with an adapter or caddy. On top of that there is one free 5.25-inch half-height external bay that can take an optical drive, a drive cage or an optional media card reader.

HP publishes no capacity ceiling for any of these; the largest drives HP shipped were 2 TB SATA hard drives and 1 TB M.2 SSDs, but larger aftermarket drives generally work — they just aren't validated by HP. If you are cloning your old drive to a new NVMe SSD, the two M.2 slots make that a simple job: put the new drive in the free slot, clone, then swap or keep both.

Buying tips: any mainstream NVMe M.2 2280 SSD works, and PCIe 3.0 means there is little point paying a premium for a PCIe 4.0 drive. For bulk storage, a SATA SSD or hard drive in the 3.5-inch bays is the cheap route.

Buying tips

  • M.2 slots take NVMe SSDs in 2280 or 2230 length
  • Assume NVMe only — M.2 SATA is not documented for these slots
  • 2.5-inch drives need a caddy for the 3.5-inch bays
  • No documented capacity limit; larger-than-factory drives usually work

Processor (CPU)

The processor is socketed (LGA1151v2) and replaceable, on the Intel Q370 chipset. HP's documentation lists 8th-generation Intel Coffee Lake-S parts only: Core i3, i5 and i7, plus Pentium Gold and Celeron. Examples on HP's list include the Core i3-8100/8300, i5-8400/8500/8600, i5-8600K, i7-8700 and i7-8700K.

The highest TDP HP supports is 95 W (the i7-8700K and i5-8600K, listed for the Workstation Edition of this same Tower platform). A 65 W chip such as the i7-8700 is the sensible upgrade for most owners — same six cores with more headroom than an i5, without pushing the cooling or power supply.

A common question is 9th-generation support. The physical socket is the same and parts like the i9-9900 will fit mechanically, but HP never listed 9th-gen CPUs for the G4 — that arrived with the G5 — and BIOS and microcode support is uncertain. Don't buy a 9th-gen chip counting on it working.

If your upgrade plans include a graphics card as well, note the power limits: the stock power supply is roughly 250 W and uses an HP-proprietary form factor, so a 95 W K-series CPU plus a modern GPU will likely need the higher-wattage supply from the 880 G4 Tower configuration or an aftermarket unit.

Buying tips

  • 8th-gen Intel Coffee Lake-S only: Core i3/i5/i7, Pentium Gold, Celeron
  • 95 W is the supported TDP ceiling; a 65 W i7-8700 is the safe pick
  • Don't buy a 9th-gen CPU — support is not confirmed
  • Factor in the ~250 W stock PSU if a GPU upgrade is also planned

How to upgrade

Before you start

  • Back up anything you care about before opening the case.
  • Shut down the PC, switch it off and unplug the power cable.
  • Ground yourself (touch the metal chassis or use an anti-static strap) before handling parts.
  • Open the case — exact disassembly steps, screws and latches are model-specific, so follow the owner's manual/service guide for this chassis.
  • Install the new part, close the case and reconnect power.
  • Start the PC and enter the BIOS/firmware setup to confirm the new memory or drive is detected, then boot into your operating system to confirm capacity.

Steps

  1. Install and verify
    Work through the checklist above. HP's Maintenance and Service Guide for the EliteDesk 800 G4 TWR / 880 G4 TWR has the illustrated disassembly and part-removal procedures for this chassis; use it for the exact screw and latch locations rather than guessing.

Good to know

  • Don't confuse the Tower with the 800 G4 SFF, Desktop Mini or 880 G4 Tower — memory, card and drive options differ.
  • 32-bit Windows cannot use more than about 3 GB of memory; 64-bit Windows is required for anything above 4 GB.
  • Capacity figures larger than HP's factory options are generally not validated by HP, even when they work in practice.

Frequently asked questions

How much RAM can the HP EliteDesk 800 G4 Tower take?

64 GB total, using four 16 GB unbuffered non-ECC DDR4 DIMMs. All four slots are user-accessible with nothing soldered. 32 GB modules are not validated for this platform, so 64 GB means 4 x 16 GB.

What RAM speed does the 800 G4 Tower support?

Up to 2666 MT/s, but only with an 8th-gen Core i5 or i7. With a Core i3, Pentium or Celeron the memory runs at 2400 MT/s. Note HP's documents disagree — the service manual says DDR4-2400 and the spec sheets say DDR4-2666 — but both work, since faster modules simply run at the slower rate.

Does the 800 G4 Tower support ECC or registered memory?

No. It requires unbuffered, non-ECC DDR4. ECC and registered/server modules are unsupported and the manual warns the system may not operate properly with them. x4-device modules are also unsupported.

How many SSDs can I install in the 800 G4 Tower?

Up to five drives in total: two M.2 NVMe SSDs (2280 or 2230, PCIe 3.0 x4) plus three SATA 6 Gb/s drives in the 2.5-inch and 3.5-inch bays. The extra M.2 slot is a PCIe x1 WLAN slot and cannot take a drive.

Does the 800 G4 Tower support 9th-gen Intel CPUs?

Not officially. HP lists 8th-generation Coffee Lake-S processors only for this machine. A 9th-gen chip such as the i9-9900 fits the socket physically, but BIOS and microcode support is uncertain, so we would not recommend buying one for this PC.

Can I upgrade the CPU?

Yes — the CPU is socketed, not soldered. HP supports 8th-gen Core i3/i5/i7, Pentium Gold and Celeron parts up to 95 W. The i7-8700 (65 W) is a popular step up; the 95 W K-series chips were offered in the Workstation Edition of this same Tower.

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.