HP launched the Z440, Z640 and Z840 together in September 2014, and more than a decade later they are still among the most widely used professional workstations in the world. Built around Intel's Xeon E5 v3 and v4 processors and DDR4 ECC memory, they came off corporate leases by the hundreds of thousands, and the refurbished market now offers them for a small fraction of what a new workstation costs.
The three share the same tool-free Z chassis design and the same processor generation, but they are sized for very different jobs. The Z440 is a single-socket tower for CAD and design. The Z640 adds a second processor on a riser in a compact chassis. The Z840 is the dual-socket flagship, with 16 memory slots, a 1125W power supply and room for three graphics cards.
This guide compares the HP Z440, Z640 and Z840 on processors, memory, graphics, storage, power and cost, and gives a clear recommendation by workload.
Understanding the HP Z G3 Workstations
All three towers use Intel's C612 chipset with LGA2011-3 processors, DDR4 ECC registered memory, PCIe 3.0 expansion and HP's tool-free, modular chassis with a front handle. What separates them is the number of processor sockets, the number of memory slots, and how much power and graphics capacity each chassis can deliver.
HP Z440 Workstation
Best ValueSingle-socket mid-tower with Intel Xeon E5-1600 v3 or v4 processors, up to 8 cores, 8 DIMM slots and up to 256GB of DDR4. The best fit for CAD, design and single-GPU work.
Sockets
1
Max cores
8
Max memory
256GB
GPU power
225W (700W PSU)
Advantages
- Lowest cost of the three on the refurbished market
- High-clock Xeon E5-1650 v4 and E5-1680 v4 suit CAD
- Eight DIMM slots, more than a single-CPU Z640
- Compact, quiet and light at about 13.5kg
- Rack-mountable in 4U with HP's rail kit
Limitations
- Single socket, 8 cores maximum
- 525W supply on some units allows only 75W of graphics
- Four memory channels
- Xeon E5 is not on Microsoft's Windows 11 processor list
HP Z640 Workstation
Best BalanceDual-socket tower in a compact chassis, with one or two Xeon E5-2600 v3 or v4 processors, up to 44 cores, 8 DIMM slots across the board and second-CPU riser, up to 256GB of DDR4 and a 925W supply.
Sockets
2
Max cores
44 (2 × 22)
Max memory
256GB
GPU power
375W total
Advantages
- Dual-CPU performance in a mid-tower footprint
- 925W supply fits two professional GPUs
- Takes the same Xeon E5-2600 v4 CPUs as ProLiant Gen9 servers
- Second CPU and memory riser can be added later
Limitations
- Only 4 DIMM slots with one CPU; 8 with the riser
- Memory tops out at 256GB, the same as the Z440
- The riser blocks the top PCIe slot
- Second-CPU riser is a separate part to find
HP Z840 Workstation
Highest PerformanceThe dual-socket flagship: two Xeon E5-2600 v3 or v4 processors, up to 44 cores, 16 DIMM slots with up to 1TB of memory, an 850W or 1125W supply and up to three graphics cards.
Sockets
2
Max cores
44 (2 × 22)
Max memory
256GB RDIMM, 1TB LRDIMM
GPU power
2 × 300W or 3 × 225W
Advantages
- 16 DIMM slots, 8 per CPU, on four channels each
- 1125W supply runs two 300W or three 225W GPUs
- Seven PCIe slots, four of them Gen3 x16 or x8
- Four 3.5-inch bays, expandable to eight 2.5-inch drives
- Eight SAS ports on board
Limitations
- Largest and heaviest: about 23kg typical
- Top CPUs need the 1125W supply
- Highest refurbished price of the three
- Memory beyond 256GB needs costly LRDIMMs
Performance Comparison
On processing power, the Z640 and Z840 are equal: both take two Xeon E5-2600 v4 CPUs with up to 22 cores each. The Z440 is limited to the single-socket E5-1600 family, which trades cores for higher clock speeds. The differences that matter most between all three are memory capacity and graphics power.
Check the power supply before you buy. A Z440 with the 525W unit has no graphics power cable and supports only 75W of graphics, which rules out most professional GPUs. The 700W unit raises that to 225W with two power cables. On the Z840, the 850W unit supports a single 150W card, while the 1125W unit supports two 300W cards or three 225W cards and is required for the top E5-2600 v4 processors.
| Specification | Z440 | Z640 | Z840 |
|---|---|---|---|
| Announced | September 2014 | September 2014 | September 2014 |
| CPU sockets | 1 | 1 or 2 | 2 |
| Processors | Xeon E5-1600 v3 / v4, select E5-2600 | Xeon E5-1600 or E5-2600 v3 / v4 | Xeon E5-2600 v3 / v4 |
| Maximum cores | 8 | 44 (2 × 22) | 44 (2 × 22) |
| Chipset / socket | C612 / LGA2011-3 | C612 / LGA2011-3 | C612 / LGA2011-3 |
| Memory channels | 4 | 4 per CPU | 4 per CPU |
| DIMM slots | 8 | 4 on board, 8 with second-CPU riser | 16 |
| Maximum memory | 256GB RDIMM | 256GB (two CPUs) | 256GB RDIMM, 1TB LRDIMM |
| Memory speed | DDR4-2133 / 2400 | DDR4-2133 / 2400 | DDR4-2133 / 2400 |
| Power supply | 525W or 700W | 925W | 850W or 1125W (1450W at 200V) |
| Graphics power | 75W (525W) or 225W (700W) | 375W total | 2 × 300W or 3 × 225W (1125W) |
| PCIe slots | 2 × Gen3 x16, 1 × Gen3 x8, 1 × Gen2 x4, 1 × Gen2 x1, 1 × PCI | Same as Z440; top slot blocked by the riser | 3 × Gen3 x16, 1 × Gen3 x8, 1 × Gen3 x4, 1 × x8 (2 CPUs), 1 × Gen2 x1 |
| Drive bays | 2 internal 3.5", 2 external 5.25", slim optical | 2 internal 3.5", 2 external 5.25", slim optical | 4 internal 3.5" (8 × 2.5" with kit), 2 external 5.25", slim optical |
| Storage ports | 6 × SATA 6Gb/s | 6 × SATA 6Gb/s | 6 × SATA and 8 × SAS 6Gb/s |
| NVMe | HP Z Turbo Drive G2 PCIe cards | HP Z Turbo Drive G2 PCIe cards | HP Z Turbo Drive G2 PCIe cards |
| Dimensions (H × W × D) | 432 × 169 × 445 mm | 445 × 172 × 465 mm | 445 × 203 × 526 mm |
| Typical weight | 13.5kg | 17kg | 22.8kg |
| Rack height | 4U | 4U | 5U |
Memory bandwidth follows the socket count. A Z440 or single-CPU Z640 has four channels. A dual-CPU Z640 or Z840 has eight, which matters for simulation and large datasets. Populate all four channels on each CPU to get it; our server RAM compatibility guide explains the population rules, which are the same as for Xeon E5 servers.
Real-World Workload Guide
The right tower depends more on the software than on the specification sheet. Most CAD modelling runs on one or two cores, while rendering and simulation use every core and memory channel available.
CAD and 3D modelling
Recommended: Z440- SolidWorks, Revit and AutoCAD favour clock speed
- Xeon E5-1650 v4 at 3.6 GHz is the sweet spot
- One professional GPU covers most models
CPU rendering and VFX
Recommended: Z640 or Z840- Blender, V-Ray and Corona scale with cores
- Two E5-2680 v4 CPUs give 28 cores
- Choose Z840 if you also need big GPUs
Simulation, FEA and CFD
Recommended: Z840- ANSYS, Abaqus and OpenFOAM need memory bandwidth
- 8 channels and 16 DIMM slots
- Room for NVMe scratch storage
GPU rendering, AI and machine learning
Recommended: Z840- Two 300W or three 225W GPUs on the 1125W supply
- 80 PCIe lanes with two CPUs
- Z440 with the 700W supply works for one GPU
Video editing and colour grading
Recommended: Z440 or Z640- The GPU does most of the work
- 8 to 16 cores covers encoding and effects
- Add a Z Turbo Drive for media cache
Office CAD, education and labs
Recommended: Z440- Lowest cost per seat
- ECC memory and pro GPU support
- Simple to upgrade as needs grow
The honest summary: the Z440 is the right workstation for most designers and engineers, the Z640 is a cost-effective route to many cores, and the Z840 is the machine for users who need large memory, several GPUs or both.
CPU Options and Upgrade Paths
These towers are inexpensive to upgrade because the Z640 and Z840 use the same LGA2011-3 Xeon E5-2600 v3 and v4 processors as HPE ProLiant Gen9 and Dell PowerEdge 13G servers, so used CPUs are plentiful. The Z440 takes the single-socket E5-1600 family, which offers the highest clock speeds of the generation.
| Tower | Good-value CPUs | High-clock CPUs | Maximum-core CPUs |
|---|---|---|---|
| Z440 (Xeon E5-1600) | E5-1620 v4 (4 cores, 3.5 GHz), E5-1650 v3 (6 cores) | E5-1650 v4 (6 cores, 3.6 GHz), E5-1680 v4 (8 cores, 3.4 GHz) | E5-1680 v4 (8 cores) |
| Z640 / Z840 (Xeon E5-2600 v3) | E5-2650 v3 (10 cores), E5-2670 v3 (12 cores) | E5-2643 v3 (6 cores, 3.4 GHz), E5-2667 v3 (8 cores, 3.2 GHz) | E5-2699 v3 (18 cores) |
| Z640 / Z840 (Xeon E5-2600 v4) | E5-2650 v4 (12 cores), E5-2680 v4 (14 cores) | E5-2643 v4 (6 cores, 3.4 GHz), E5-2667 v4 (8 cores, 3.2 GHz) | E5-2697 v4 (18 cores), E5-2699 v4 (22 cores) |
Before upgrading, update the BIOS: v4 processors need a newer BIOS than the one these towers shipped with. Both CPUs in a dual-socket tower must be the same model, and a Z640 needs the second-CPU-and-memory riser to add a processor. On the Z840, the E5-2699 v4, 2697 v4, 2695 v4 and 2687W v4 require the 1125W power supply. Windows 10 is fully supported; Xeon E5 processors are not on Microsoft's Windows 11 list, so Linux or Windows 10 LTSC are the long-term options.
ServerDove stocks Xeon E5 v3 and v4 processors for these towers, along with ECC DDR4 memory and graphics cards.
How They Compare with Other Workstations
The Z440, Z640 and Z840 sit between HP's DDR3-based Z420, Z620 and Z820 and the Z4, Z6 and Z8 G4 that replaced them in 2017. Dell's Precision T5810, T7810 and T7910 are the direct competitors from the same generation.
| Class | Previous HP (2012) | HP Z G3 (2014) | Dell Equivalent (2014) | HP Successor (2017) |
|---|---|---|---|---|
| Single socket | Z420 (Xeon E5 v1/v2, DDR3) | Z440 (Xeon E5-1600 v3/v4) | Precision T5810 | Z4 G4 (Xeon W-2100/2200) |
| Dual socket, compact | Z620 (Xeon E5 v1/v2, DDR3) | Z640 (Xeon E5-2600 v3/v4) | Precision T7810 | Z6 G4 (Xeon Scalable) |
| Dual socket, flagship | Z820 (Xeon E5 v1/v2, DDR3) | Z840 (Xeon E5-2600 v3/v4) | Precision T7910 | Z8 G4 (Xeon Scalable) |
Compared with the earlier Z420 and Z820, the G3 towers bring DDR4, more cores per socket, PCIe NVMe storage and current GPU support. Compared with the Z4, Z6 and Z8 G4, they lack the newer Xeon W and Xeon Scalable processors and Windows 11 support, but cost far less. If you are also considering Dell, our Dell Precision T5820 vs T7820 vs T7920 guide covers the next generation of Dell towers.
Cost vs Performance: Which Should You Choose?
On the refurbished market, the Z440 is the least expensive of the three, the Z640 costs moderately more, and the Z840 carries a premium for its chassis, 1125W supply and expansion. Xeon E5 v4 processors and DDR4 RDIMMs are now very cheap, so the best value usually comes from choosing the right chassis and configuring it generously.
Choose the Z440 if…
- Your main work is CAD or design
- One GPU is enough
- 256GB of memory covers your data
- Budget per seat matters most
Choose the Z640 if…
- You need many CPU cores
- Desk space is limited
- Two mid-range GPUs is enough
- You want to add a second CPU later
Choose the Z840 if…
- You need two CPUs and big GPUs
- Memory needs exceed 256GB
- You run three GPUs or many drives
- You want SAS storage on board
When buying refurbished, confirm the power supply rating, whether the Z640 has its second-CPU riser, how many DIMM slots are populated, and the BIOS version. A Z440 with the 525W supply cannot run a professional GPU above 75W, and a single-CPU Z640 needs the riser to add a processor. Our refurbished hardware inspection checklist covers what to test on arrival.
Future Trends
HP's workstation line has moved on twice since the G3 generation, and the refurbished market follows a few years behind each change.
Z420 / Z620 / Z820
2012
Xeon E5 v1 / v2, DDR3
Budget RefurbZ440 / Z640 / Z840
2014
Xeon E5 v3 / v4, DDR4-2400
Refurb Sweet SpotZ4 / Z6 / Z8 G4
2017
Xeon W and Scalable, DDR4-2933
Mid-Price RefurbZ4 / Z6 / Z8 G5
2023
Xeon W-2400 / 3400, DDR5, PCIe 5.0
CurrentTwo trends matter for buyers. First, the GPU now does most of the heavy lifting in rendering, AI and video work, so a G3 tower with a modern professional graphics card remains highly capable. Second, as the Z G4 generation reaches the refurbished market in volume, prices for the Z440, Z640 and Z840 continue to fall, making them exceptional value for businesses that do not need Windows 11 or DDR5.
Conclusion
The HP Z440 is the right choice for most CAD, design and video users: a single high-clock Xeon E5-1600 v4, up to 256GB of ECC memory and a professional GPU at the lowest cost. The Z640 delivers up to 44 cores in the same compact footprint, ideal for CPU rendering when graphics needs are modest.
The Z840 is the workstation for the heaviest work. With 16 memory slots, up to 1TB of memory, an 1125W supply, three GPUs and SAS storage on board, it handles simulation, multi-GPU rendering and AI development that would overwhelm the smaller towers.
Match the tower to your software: Z440 for clock speed, Z640 for cores in a compact case, Z840 for memory and GPUs. Contact ServerDove for refurbished HP Z workstations configured to your workload, with delivery across Qatar. Request a Quote · Z440 · Z640 · Z840
