HP ProDesk 400 G9 SFF Upgrade Guide: RAM, SSD and CPU

Lifecycle and support

No lifecycle information available.

RAM: two full-size UDIMM slots

The memory is not soldered. Both slots are user-accessible and take full-size desktop UDIMMs, not laptop SO-DIMMs. HP lists configurations from 4 GB up to 64 GB, using two 32 GB modules at most.

Depending on your SKU, the memory is either DDR4-3200 or DDR5, and the two types do not fit each other's slots. HP's documents show both a DDR4-3200 configuration and a DDR5-4800 configuration. They don't say which processors go with which memory type, so check the label on your existing modules or the spec sheet for your exact configuration.

On speed, HP's documents disagree a little. Some list DDR5-5600 modules, but HP's support page says these run at up to 4800 MT/s. Plan on 4800 MT/s for DDR5. If you mix modules of different speeds, the system runs at the lower one.

Buying tips

• Confirm DDR4 or DDR5 for your unit before ordering.
• Buy non-ECC unbuffered UDIMMs. Registered modules aren't listed, and SO-DIMMs are for HP's Mini and All-in-One models, not this one.
• Buy a matched pair if you can, so both modules run at the same speed.
• Two 32 GB modules give the 64 GB maximum; one module leaves a slot free for later.

Storage: M.2 NVMe, optional M.2 2230 and a 3.5-inch SATA bay

The main upgrade path is the M.2 2280 slot, which is PCIe x4 NVMe. Some SKUs ship with Gen4 SSDs. HP's largest factory option is 2 TB, and no maximum capacity is documented, so larger drives are untested rather than ruled out.

There is also an optional M.2 2230 slot on PCIe x1, which HP describes as for WLAN/Bluetooth or storage. It may already hold your Wi-Fi card, which would leave just the one M.2 slot for a fast SSD. This detail isn't confirmed from an HP service manual.

A 3.5-inch internal SATA bay holds a hard drive; HP offers 1 TB and 2 TB 7200 RPM models. The board has 3 SATA ports in total. No 2.5-inch bay is listed for this model, so a 2.5-inch SSD would need an adapter. The optical drive bay and SD card reader are options that had to be ordered with the PC, so don't assume your unit has them.

If you use HP's DriveLock feature, note that it does not work with self-encrypting (OPAL2) SSDs.

Buying tips

• For the best speed, choose an M.2 2280 NVMe SSD.
• Open the case and check what's in the 2230 slot before planning to use it.
• A 3.5-inch drive is the simple SATA option. A 2.5-inch drive needs a mounting adapter.
• Avoid self-encrypting (OPAL2) SSDs if you rely on DriveLock.

CPU: Intel Core 12th to 14th gen

This PC uses the Intel Q670 chipset and supports 12th, 13th and 14th gen Core processors, plus Pentium Gold G7400, Celeron G6900 and the Core 300 line. HP's support page lists the Core i7-14700 as the top option. Low-power T variants such as the i7-12700T and Celeron G6900T are also offered.

HP's documents don't name the socket; a Q670 board with 12th to 14th gen desktop Core CPUs uses LGA1700, so look for that when shopping. HP doesn't publish a maximum CPU power rating either, but the internal power supply is 240 W, which limits how power-hungry a processor (or a graphics card) you can run. Stay within the processors HP lists for this model.

HP's own documents also disagree slightly: the Core i5-14600 appears in one retailer brochure but not in the support page's processor list. A BIOS update may be needed before a newer CPU will work.

Buying tips

• Stick to processors named on HP's support page for this model.
• Look for LGA1700 and the 12th to 14th gen Core family.
• Avoid chips that draw much more power than the i7-14700 given the 240 W supply.
• Check for the latest BIOS before swapping in a newer CPU.

How to upgrade

Before you start

• Find out whether your PC uses DDR4 or DDR5 memory, and check which modules are installed.
• Back up your important files.
• Have the owner's manual or HP's support page for your model to hand for exact disassembly instructions.
• Note that the optical drive bay and SD reader are optional, so check what your unit actually has.
• If you plan to change the CPU, check HP's support page for a newer BIOS first.

Steps

1. Back up your data
   Copy important files to an external drive or cloud storage, especially before changing a drive or the CPU.
2. Power off and unplug
   Shut the PC down fully, then unplug the power cable and any other connected cables. Hold the power button briefly to discharge leftover power.
3. Ground yourself
   Work on a clean, hard surface and touch bare metal on the case before handling parts. Hold components by their edges.
4. Open the case
   Follow the owner's manual for removing the side panel and any internal covers or brackets. The exact latches and screws vary, so use HP's instructions rather than guessing.
5. Install the new part
   For RAM, fit full-size UDIMMs of the right DDR type into the DIMM slots. For an SSD, use the M.2 2280 slot, or fit a SATA drive in the 3.5-inch bay. For a CPU, use a compatible processor and follow HP's guidance on the cooler and power limits.
6. Close the case and reconnect
   Refit all covers, then reconnect the cables and power.
7. Check the BIOS
   Switch on and open the BIOS setup. Confirm that the new memory, drive or processor is detected. If a new CPU isn't recognised, check for a BIOS update. A new SSD may also need an operating system installed.

Good to know

• We couldn't find an HP service manual for this model, so some details, such as the contents of the M.2 2230 slot and the exact CPU socket, are unconfirmed.
• HP's documents disagree on top DDR5 speed (5600 vs 4800 MT/s). Expect 4800 MT/s.
• HP's pages disagree on the PCIe expansion slot versions: one says both are v4.0, another lists PCIe 3 for the x1 slot.
• The optical drive bay and SD card reader are factory options, so your unit may not have them.
• Several HP documents cover multiple chassis, and some details (such as the 2.5-inch SATA note) apply to the Mini, not the SFF.
• Check the exact model and SKU of your PC before buying parts.

Frequently asked questions

How much RAM can the HP ProDesk 400 G9 SFF take?

Up to 64 GB, using two 32 GB UDIMMs. HP lists configurations from 4 GB upward.

Does the ProDesk 400 G9 SFF use DDR4 or DDR5?

It depends on the SKU. HP documents both DDR4-3200 and DDR5 models, and the two are not interchangeable, so check your current modules or spec sheet before buying.

Can I use laptop SO-DIMM memory?

No. The SFF uses full-size non-ECC unbuffered UDIMMs. SO-DIMMs are for HP's Mini and All-in-One versions.

Can I add a second SSD?

Possibly. There is an optional M.2 2230 slot (PCIe x1) for WLAN or storage, but it may already hold your Wi-Fi card. You can also add a SATA drive in the 3.5-inch bay.

Can I install a 2.5-inch SSD?

No 2.5-inch bay is listed for this model. You would need an adapter to mount a 2.5-inch drive in the 3.5-inch bay.

What is the best CPU I can fit?

HP's support page lists the Core i7-14700 as the top option. The power supply is 240 W, so high-power processors are limited, and a BIOS update may be needed for newer CPUs.

Official documents and references

• HP support page for the Pro SFF 400 G9
  Official memory, storage, processor and expansion specs
• HP Middle East product specifications
  Memory, storage and 240 W power supply details
• PDF Pro 400 G9 SFF datasheet
  SFF datasheet with UDIMM memory details
• PDF HP manufacturer brochure
  Example DDR4 and DDR5 configurations and non-ECC options
• PDF HP Pro Series 400 G9 desktops datasheet
  Covers all four chassis, so check which cells apply to the SFF