HP EliteDesk 800 G5 Tower PC 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.

Memory (RAM)

What fits: four 288-pin DDR4 UDIMM slots, non-ECC and unbuffered only. That means ordinary desktop memory modules — not the short SO-DIMMs used in laptops and not server (ECC or registered) memory. x8 and x16 modules are fine; x4-wide DIMMs are explicitly not supported. Single- and double-sided modules both work. There is no soldered memory, so all four slots are yours to use.

How much: 32 GB per module, so 4 x 32 GB = 128 GB in theory. Here HP's documents disagree, and it's worth knowing before you spend money: the Maintenance & Service Guide and the Hardware Reference Guide say 64 GB maximum, while the quickspecs say 128 GB with 4 x 32 GB. The manual text is older boilerplate, and 32 GB dual-rank UDIMMs do work in these boards. If HP support quotes 64 GB, that's the outdated figure.

Speed: DDR4-2666 MT/s is the ceiling, and the actual speed depends on the CPU. With an 8th/9th Gen Core i5, i7 or i9 you get DDR4-2666; with a Core i3, Celeron or Pentium the memory controller tops out at DDR4-2400, so faster modules simply run slower. Faster RAM won't hurt, but it won't help either.

What to watch out for: many units ship with a single module running single-channel, which noticeably hurts the integrated UHD 630 graphics. Buy memory in matched pairs (same size and speed) and populate the slots for dual-channel. Also check which CPU you have before paying a premium for 2666-rated modules.

Buying tip: look for DDR4-2666 CL17 UDIMM kits with JEDEC SPD — the modules HP specifies are standard 1.2 V desktop memory with mandatory SPD, so exotic overclocking memory with non-standard timings isn't necessary here.

Buying tips

• Matched pairs of desktop DDR4 UDIMM, non-ECC unbuffered
• DDR4-2666 for i5/i7/i9, DDR4-2400 is enough for i3/Celeron/Pentium
• Avoid x4-wide DIMMs, ECC and registered/server memory

Storage

What fits: two M.2 slots for storage, both accepting 2230 or 2280 size NVMe drives. A third M.2 2230 slot is for the WLAN card only — a drive won't work there. The SATA side of the board offers 2.5" and 3.5" bays for SATA SSDs and hard drives, and the system board has SATA power and a SATA port documented. There is also an external 5.25" optical bay on builds that have the optical drive option.

Interface details: the M.2 storage slots are PCIe NVMe (PCIe 3.0 generation). Whether SATA-protocol M.2 drives work is not confirmed in the available documentation, so assume NVMe and you won't be disappointed. Intel Optane was a factory option, including the Optane Memory H10.

Capacity: HP's quickspecs list factory drives up to 2 TB (2 TB TLC NVMe, 2 TB 7200 rpm HDD), but no document states a hard maximum, and modern drives larger than those factory options may well work. If you want a very large drive, check the current HP documentation or ask HP directly rather than assuming a limit.

What to watch out for: the exact number of SATA bays, the 2.5" drive thickness limit and whether caddies or brackets are included are not listed in the available pages — the Maintenance & Service Guide has the drive-bay chapter and is the place to confirm before ordering a drive or a caddy. Also remember the M.2 slots and the SATA drives share chipset lanes, and the second PCIe x16-length slot is electrically wired x4, so heavy multi-drive setups can hit bandwidth limits. The optional 5-in-1 SD reader is not present on all builds.

Buying tip: an M.2 2280 NVMe SSD is the simplest big upgrade — it needs no cables and no caddy, and it slots straight into one of the two storage M.2 positions. Check the manual for which slot is easiest to reach.

Buying tips

• M.2 2280 NVMe SSD — no cables, no caddy needed
• SATA drives: confirm bay count and caddy requirements in the service guide first
• Treat SATA M.2 support as unconfirmed and buy NVMe

Processor (CPU)

What fits: one LGA 1151 (Socket H4) processor, Coffee Lake generation, on the Intel Q370 platform. This is a socketed CPU, so it can be replaced — but only within the 8th and 9th Gen families. The socket looks the same as the older 6th/7th Gen LGA 1151 chips, and those older processors will not work here. Supported parts are 8th Gen Core i3-8100, i5-8500 and i7-8700, plus 9th Gen Core i3-9100/9300, i5-9500/9600/9600K, i7-9700/9700K and i9-9900/9900K, along with Celeron G4930 and Pentium Gold G5420/G5600/G5620.

Power limit: the tower chassis supports up to 95 W, which covers the unlocked K-series parts (i5-9600K, i7-9700K, i9-9900K). The standard chips are 65 W. The 95 W K-series parts are listed as tower-only — the smaller EliteDesk 800 G5 variants use 65 W and 35 W processors instead.

What to watch out for: 9th Gen processors may need a BIOS update on early-production boards, so update the firmware before swapping in the new CPU if your board is an early one. With a 95 W K-series chip on the stock cooler, expect more noise and possibly marginal cooling; the stock cooler is designed around the standard parts. If you're also adding a graphics card, keep an eye on power supply headroom. And note that the Celeron and Pentium configurations were sold as Windows 10-only systems.

Buying tip: for most owners the jump to a used Core i7-8700 or i7-9700 is the sweet spot — no cooling or power worries, and DDR4-2666 support. Only chase the K-series chips if you want the last few percent and are prepared for fan noise.

Buying tips

• 8th/9th Gen Coffee Lake only — 6th/7th Gen LGA 1151 chips will not work
• 65 W parts are the safe choice; 95 W K-series is supported but louder
• Update the BIOS first if you're going to a 9th Gen CPU

How to upgrade

Before you start

• Back up your data before touching anything.
• Shut down, switch off at the PSU if it has a switch, and unplug the power cable and everything else.
• Ground yourself — touch the metal chassis or use an anti-static strap — so static doesn't damage the board.
• Open the case. The exact release points, screws and latches differ between builds, so follow the owner's manual for disassembly rather than forcing anything.
• Install the new part, making sure memory modules click fully home and M.2 drives sit flat before securing them.
• Close the case and reconnect the cables.
• Power on and check in the BIOS/firmware that the new memory, drive or processor is recognised, then boot into your operating system.

Steps

1. Back up
   Save anything you care about before you start. Upgrades are usually painless, but a backup costs nothing.
2. Power down and unplug
   Shut the PC down normally, switch the PSU off if it has a switch, then unplug the mains lead and all peripherals.
3. Ground yourself
   Work on a hard, non-carpeted surface. Touch the metal chassis before handling components, or wear an anti-static strap.
4. Open the case
   Follow the owner's manual for the exact opening procedure and for where the screws or release points are. Don't force panels or latches.
5. Install the upgrade
   Seat the module or drive firmly — memory should click into both clips, and an M.2 drive should lie flat before you secure it. If you're swapping the CPU, update the BIOS first when moving to a 9th Gen chip.
6. Close up and check
   Refit the panels, reconnect the power, then start the PC and confirm in the BIOS/firmware that the new memory, drive or CPU is detected before booting into Windows.

Good to know

• This guide covers the Tower (TWR/MT) chassis only.
• HP's documents disagree on the maximum RAM: 64 GB in the service manuals, 128 GB in the quickspecs.
• SATA M.2 drive support is unconfirmed.
• Drive bay counts, thickness limits and caddies should be verified in the Maintenance & Service Guide.
• Exact disassembly steps vary by build — use the owner's manual.

Frequently asked questions

How much RAM can the HP EliteDesk 800 G5 Tower take?

Four DDR4 UDIMM slots, 32 GB per module. The quickspecs say 128 GB total; the Maintenance & Service Guide and Hardware Reference Guide say 64 GB. The manuals' 64 GB figure is older boilerplate — 32 GB modules do work — but if you want to be certain, treat 128 GB as the later, correct spec and the manual figure as outdated.

What RAM does the EliteDesk 800 G5 Tower use?

288-pin DDR4 desktop UDIMM, non-ECC and unbuffered, up to DDR4-2666 (DDR4-2400 with Core i3, Celeron and Pentium processors). Not SO-DIMM, not ECC or registered, and not x4-wide modules. Buy matched pairs for dual-channel.

Does it support NVMe SSDs?

Yes. There are two M.2 2230/2280 slots for storage, and they take PCIe NVMe drives (PCIe 3.0 generation). A third M.2 2230 slot is for the WLAN card only. Support for SATA-protocol M.2 drives is unconfirmed, so stick to NVMe.

Which CPUs are supported?

8th and 9th Gen Coffee Lake processors on LGA 1151: Core i3-8100, i5-8500, i7-8700, Core i3-9100/9300, i5-9500/9600/9600K, i7-9700/9700K, i9-9900/9900K, plus Celeron G4930 and Pentium Gold G5420/G5600/G5620. 6th and 7th Gen LGA 1151 chips will not work despite fitting the socket. The tower handles up to 95 W, so the K-series parts are supported.

Do I need a BIOS update to upgrade the CPU?

Possibly. 9th Gen processors may need a BIOS update on early-production boards, so update the firmware before installing the new chip. Check that the BIOS sees the processor afterwards.

How many drives can I fit?

Two M.2 storage drives (2230 or 2280 NVMe) plus 2.5"/3.5" SATA drives in the bays. The exact SATA bay count, the 2.5" thickness limit and caddy requirements aren't listed in the available pages — confirm them in the Maintenance & Service Guide before ordering. The 5.25" optical bay and SD reader were optional, so not all builds have them.

Official documents and references

• PDF HP EliteDesk 800 G5 Tower PC — Maintenance & Service Guide (disassembly, drive bays, memory and CPU service procedures)
  Also covers the EliteDesk 880 G5 Tower; the layout matches the 800 G5 Tower.
• PDF HP EliteDesk 800 G5 Tower PC — Quickspecs (factory options, 128 GB memory figure, supported CPUs, storage list)
  
• PDF HP EliteDesk 800 G5 — options and specification sheet (M.2 slots, expansion slots)
  
• PDF HP EliteDesk 800 G5 datasheet (CPU options and TDP limits by chassis)
  Useful for confirming the 95 W K-series parts are tower-only.
• PDF HP EliteDesk 800 G5 — reference document (supported processor list)