HP Z4 G4 Tower Workstation upgrade guide

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

The HP Z4 G4 Tower Workstation (also written as Z4G4) is a friendly machine to upgrade: eight RAM slots, room for several drives and a socketed CPU. But there is one big catch you need to know before buying anything: two effectively different platforms ship under this name. One is an Intel C422 board with a Xeon W processor, the other is an Intel X299 board with a Core X-series processor. They use different memory types, different CPUs and even a different number of M.2 slots. Parts that work on one variant are not necessarily compatible with the other, so identify your variant first (your CPU name tells you: Xeon W means C422, Core i7/i9 X-series means X299). Note also that the workstation is discontinued — HP Japan ended sales on 2023-07-20 — so most parts now come from the used market.

At a glance

  • 8 DDR4 DIMM slots: up to 256 GB with Xeon W (ECC RDIMM) or 128 GB with Core X (non-ECC UDIMM)
  • SATA and M.2 NVMe storage: 2 internal 3.5" bays, 2 external 5.25" bays, 6 SATA ports, and 1 or 2 M.2 slots depending on variant
  • Socketed Intel LGA2066 R4 CPU: Xeon W-2100 (and possibly W-2200) on C422 boards, Core X-series on X299 boards, up to 165 W
8x DDR4 DIMM (ECC RDIMM Xeon / non-ECC UDIMM Core X)8 × DDR4 DIMM · up to 256 GB total · 2666 MT/s
3.5"/5.25" bays, 6x SATA, 1-2x M.2 NVMe (2.5" adapter)2 × SSD / HDD 2.5" / 3.5" / M.2 2260 / M.2 2280 / M.2 22110 (SATA / NVMe / SAS)
Intel LGA2066 R4, 1 socket (C422 / X299)LGA3647 / LGA4189 / LGA4677 · Xeon E-2100/2200, Xeon E-2100/2200, Core 8th gen, Core 9th gen · max 165 W
CPU · LGA3647,LGA4189, LGA4677max 165 W8 × DIMM · DDR4up to 256 GB total3.5"/5.25" bays, 6x SATA,1-2x M.2 NVMe (2.5" adapter)2 × SSD / HDD 2.5" / 3.5" / M.2 2260 /M.2 2280 / M.2 22110 (SATA / NVMe / SAS)
Schematic of the upgradeable slots (not to scale). Check the owner's manual for their exact positions.

Lifecycle and support

A current model: sold new and supported.

20172018201920202021202220232024202520262027Today11 · Release · November 2017
Filled dots: dates published by the manufacturer. Hollow dots: estimates from third-party sources.
MilestoneDate
Release
First available to buy.		 November 2017 Estimate HP press release: "HP Z4 Workstation is scheduled for availability in November starting at $1,239." (month precision only; announced 2017-09-13 at IBC)
Source ↗

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

Memory (RAM)

What fits

The Z4 G4 has 8 full-size DDR4 DIMM slots (4 memory channels, 2 DIMMs per channel) and no soldered memory. Memory type depends entirely on your variant:

Xeon W (C422) boards accept only registered ECC RDIMMs, in 8 GB, 16 GB and 32 GB modules.

Core X-series (X299) boards accept only non-ECC UDIMMs, in 8 GB and 16 GB modules.

This is the single most common buying mistake: the wrong memory type simply will not POST. Buy RDIMM for Xeon configs, UDIMM for Core X configs, and don't mix types.

Limits

Speeds are DDR4-2666 / 2400 / 2133 MT/s, but the actual speed is set by your CPU — Xeon W-2102 and W-2104 cap memory at 2400 MT/s no matter how fast the DIMMs are rated.

Maximum total capacity is 256 GB (8 x 32 GB RDIMM) on Xeon configs and 128 GB (8 x 16 GB UDIMM) on Core X configs. You may see a "512 GB max memory" line in Xeon W-2100 processor specs; that is the chip's capability, not what HP validated for this board. Plan on 256 GB.

What to watch out for

32 GB RDIMMs require the HP Z4 Memory Cooling Solution (CTO 1MY90AV / AMO 1XM34AA). Without that fan and shroud, 32 GB modules can throttle or fault. If you are buying 32 GB sticks used, budget for finding that cooling kit too.

For best performance, populate at least one DIMM per channel — filling slots in pairs or quads gives full bandwidth.

Buying tips

Identify your CPU first, then buy the matching memory type. Match the rated speed to what your CPU supports rather than paying for faster modules you can't use.

Buying tips

  • Check whether your machine is a Xeon W (ECC RDIMM) or Core X (non-ECC UDIMM) config before ordering RAM — they are not interchangeable.
  • 32 GB RDIMMs need HP's memory cooling solution; 8 GB and 16 GB modules do not have that requirement.
  • Buy 2666 MT/s modules at most, and only if your CPU supports it — W-2102/W-2104 stop at 2400 MT/s.

Storage (SSD and HDD)

What fits

The system board provides 6 SATA (6 Gb/s) ports, and there is M.2 NVMe support as well:

M.2 Slot 1: PCIe Gen3 x4, NVMe, from the CPU. Lengths are listed as 2260 / 2280 / 22110 in the system-board section of HP's documentation, though the same document also describes support as "up to 80 mm".

M.2 Slot 2: also PCIe Gen3 x4 NVMe from the CPU, but only on Xeon W configs. On Core X configs HP states plainly that no second M.2 connector is available.

For physical drives there are 2 internal 3.5" bays (with dampened carriers) and 2 external 5.25" bays. There are no native 2.5" bays — 2.5" SSDs and HDDs need a bracket or carrier. A 3rd or 4th 3.5" HDD each eats one of the external 5.25" bays, giving up to 4 x 3.5" drives at the cost of both external bays; two 2.5" drives can share a single external bay with a 2:1 carrier. SAS drives are supported only on Xeon configs and only with an add-in SAS controller card — there is no onboard SAS.

Limits

No drive-size cap is documented. HP's own options topped out at 6 TB SATA HDDs and 2 TB SATA SSDs; larger commodity SATA and NVMe drives generally work but are not HP-validated.

What to watch out for

The M.2 length question is genuinely unclear: one part of HP's documentation lists 22110 (110 mm) support, another says up to 80 mm. A 2280 (80 mm) drive is the safe bet. Before buying a 22110 drive, check that your board actually has the 110 mm standoff.

Some Core i7 X-series configs have a PCIe slot 3 that is only x8 electrically and a slot 5 that is mechanical only (no data), which makes those machines poor candidates for add-in NVMe or HBA cards. PCIe Gen3 x16 slots on other configs can host storage cards, though full-length, full-height cards need an extender.

Buying tips

A single M.2 NVMe SSD is the cleanest upgrade on either variant. If you want a second M.2 drive, confirm you have a Xeon config first.

Buying tips

  • Buy 2280 M.2 drives unless you have physically verified the 22110 standoff.
  • 2.5" SSDs need an adapter bracket or carrier — none are native.
  • Second M.2 slot = Xeon configs only; Core X configs have one.
  • SAS drives mean a Xeon config plus a SAS add-in card — it is not built in.

Processor (CPU)

What fits

The CPU is socketed and user-replaceable: a single Intel LGA2066 R4 socket. Which processors fit depends on the chipset variant, and the two are not cross-compatible:

C422 boards take Intel Xeon W-2100 family processors (Skylake-W): W-2102, W-2104, W-2123, W-2125, W-2135, W-2145, W-2175 and W-2195, up to 18 cores / 36 threads.

X299 boards take Intel Core X-series processors (Skylake-X and Cascade Lake-X): i7-7800X, i7-7820X, i9-7900X, i9-7920X, i9-7940X, i9-7960X, i9-7980XE, i7-9800X, i9-9820X, i9-9920X and i9-9980XE, also up to 18 cores / 36 threads.

There is one source disagreement to be aware of: HP Japan's product page describes the Z4 G4 as shipping with Xeon W-2200 family processors (up to 10 cores), which appears to reflect later refreshed configurations. The original QuickSpecs list W-2100 and Core X. If you are considering a W-2200 chip, verify your exact board and BIOS revision first — this has not been confirmed to work on all units.

Limits

Maximum supported TDP is 140 W for Xeon configs (W-2145 / W-2175 / W-2195) and 165 W for high-end Core X configs (Core i9 X-series and i7-9800X).

What to watch out for

The CPU you choose locks in your memory type: a Xeon W chip means ECC RDIMMs, a Core X chip means non-ECC UDIMMs. Remember also that entry Xeon chips (W-2102, W-2104) cap memory speed at 2400 MT/s, so a "free" used upgrade to one of those can actually slow your RAM.

Buying tips

Buying a used Xeon W-2145 or better is a straightforward upgrade path on C422 boards. Whatever you buy, check the board and BIOS revision before paying, especially for any W-2200 part.

Buying tips

  • Identify your chipset first: C422 = Xeon W, X299 = Core X. CPUs are not interchangeable between them.
  • Stay within 140 W (Xeon) or 165 W (Core X) TDP.
  • Confirm board and BIOS revision before buying a used CPU, particularly W-2200 parts.
  • Avoid W-2102/W-2104 as upgrades — they cap RAM at 2400 MT/s.

How to upgrade

Before you start

  • Back up your data before touching any hardware.
  • Power off the workstation completely and unplug the power cable.
  • Ground yourself to avoid static damage — use an anti-static strap or touch the metal chassis before handling parts.
  • Open the case and install the component (RAM, M.2/SSD or CPU). For exact disassembly, screw locations and the CPU cooler procedure, follow the HP owner's manual for the Z4 G4.
  • Close the case, reconnect the power and switch on.
  • Enter the BIOS/firmware to confirm the new part is detected at the expected size and speed, then let your operating system recognise it.

Good to know

  • The Z4 G4 is discontinued (HP Japan sales ended 2023-07-20), so new CTO parts are gone and used-market stock and remaining warranty vary.
  • HP's documentation is inconsistent about M.2 drive length: 2260 / 2280 / 22110 in the system-board section, but "up to 80 mm" elsewhere. Verify the standoff on your unit before buying a 110 mm drive.
  • HP's documents describe the machine with both Xeon W-2100 / Core X CPUs (original QuickSpecs) and Xeon W-2200 CPUs (HP Japan page, later configs). Check your exact board and BIOS revision before buying a CPU.

Frequently asked questions

How much RAM can the HP Z4 G4 take?

Up to 256 GB (8 x 32 GB registered ECC RDIMMs) on Xeon W configs, and up to 128 GB (8 x 16 GB non-ECC UDIMMs) on Core X configs. A 512 GB figure appears in Xeon processor specs, but HP validated the board only to 256 GB.

Does the HP Z4 G4 support ECC memory?

Yes, but only on Xeon W (C422) configs, which require registered ECC RDIMMs. Core X (X299) configs use non-ECC UDIMMs only. The wrong type will not POST.

Can I add a second M.2 SSD?

Only if you have a Xeon W config. HP states that no second M.2 connector is available on Core X-series configs, which have a single M.2 slot.

Which CPUs fit the HP Z4 G4?

Any Intel LGA2066 R4 chip from the matching platform: Xeon W-2100 family on C422 boards, or Core X-series (Skylake-X / Cascade Lake-X) on X299 boards. HP Japan also lists later configs with Xeon W-2200 up to 10 cores, but verify your board and BIOS revision first. Maximum TDP is 140 W (Xeon) or 165 W (Core X).

Do I need anything special for 32 GB memory modules?

Yes. HP requires the Z4 Memory Cooling Solution (1MY90AV / 1XM34AA) for 32 GB RDIMM configurations. Without it, the system may throttle or fault.

Does the HP Z4 G4 support SAS drives?

Only on Xeon W configs, and only with an add-in SAS controller card — SAS is not built into the system board.

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.