By dedicating a high GHz workstation to CAD and a dual Xeon box to rendering, designers can have optimised hardware for both processes. The workflow benefits can be huge, but the package doesn’t come cheap, writes Greg Corke.

Ray trace rendering is arguably the most computationally intensive process in any architectural design workflow. It is highly multi-threaded so it absolutely hammers all of a workstation’s CPU cores. It is also extremely scalable, so doubling the number of cores can, in many cases, halve the render time.

Most CAD software is very different in that it is a single-threaded process, so the majority of tasks are performed on one CPU core. This means it thrives on a high-frequency (GHz) CPU. Performance will not increase if you add more CPU cores.

This presents a big challenge when choosing a workstation for both CAD and rendering. The highest frequency CPUs have the least number of cores, while the ones with the most cores tend to have the lowest frequencies.

As a result, architects and engineers must accept that there will always be a trade-off — or must they?

Custom workstation manufacturer BOXX offers an alternative solution by dedicating separate machines to each process. CAD work is done on the BOXX APEXX 2, a high-frequency Intel Core i7 desktop workstation, while the rendering is handled by the BOXX renderPRO 2, a networked, dual Intel Xeon rendering machine with lots of cores.

As both machines work completely independently of each other, it also means that the BOXX APEXX 2 workstation is able to dedicate almost all of its resources to CAD modelling when the BOXX renderPRO 2 is rendering.

In contrast, when a traditional desktop workstation is set to render flat out, it will often become sluggish, making it almost impossible to do any meaningful CAD work.

There are ways to get around this. Users can reduce the number of cores assigned to the rendering task, either by changing processor affinity in Windows Task manager (so specific applications use specific CPU cores) or by applying more granular control of CPU core usage inside the rendering application. But that means renders come back slower.

The BOXX renderPRO 2

The renderPRO 2 has the same footprint as a dual Intel Xeon desktop workstation, such as the BOXX APEXX 4, but it is only about one fifth of the height.

BOXX pitches the machine as a personal rendering solution, designed to sit on a desk or on top of a workstation (although it is too big to sit on top of the APEXX 2). Multiple units can also be stacked on top of each other.

This is all great in theory, but if like me you place a great value on a calm working environment, you are much better off putting this networked machine well away from where you sit.
With two high-end Xeon CPUs running flat out and heavy-duty fans to cool them, the heat and noise the machine gives off, even when idle, is significant.

Our test machine was kitted out with two Intel Xeon E5-2650 v4 CPUs, each of which has 12 cores (24 threads) and a clock speed of 2.2GHz (Turbo to 2.9GHz). On test, with all 48 cores running flat out, these ran at 2.5GHz.

Higher-end CPUs are also available, up to the Intel Xeon E5-2695 v4 (18 cores, 2.1GHz up to 3.3GHz), at a premium.

With 64GB of memory, our test machine could easily store everything we threw at it, but those with more demanding datasets can expand this to a maximum of 256GB.

Storage is courtesy of a single 2.5-inch 240GB SATA SSD. Other capacities are available, up to 1.2TB, and it is also possible to add a second drive. The machine has on-board graphics, so you can plug in a monitor via the VGA port, but most users will likely access the machine remotely.

The BOXX APEXX 2 (model 2402)

The APEXX 2 is a beautifully engineered, solid, compact single-CPU workstation. The machine is built around a quad core Intel Core i7-6700K, which is permanently overclocked to 4.4GHz, making it perfect for frequency-hungry CAD applications.

To keep the machine running at this speed, the CPU is liquid cooled. This not only brings stability to the system, but also helps keep noise to a minimum. With two low-duty fans at the front of the workstation, it is extremely quiet in operation, even under very heavy loads. It is the polar opposite to the renderPRO 2.

The rest of the specifications are also well-matched for high-end CAD and design viz workflows. The Nvidia Quadro M4000 GPU should provide more than enough 3D graphics performance for CAD and BIM software, but users of design viz applications such as 3ds Max may be better served by the more powerful Quadro M5000 or M6000. However, with both of these high-end GPUs set to be replaced by the Quadro P5000 and P6000 in October, it is worth holding out.

For most mainstream workflows, 32GB of DDR4 memory should be plenty. This can be expanded to 64GB if required, but with all four DIMM slots already full, this should be done at time of purchase.

Storage is courtesy of a 512GB Samsung SM951 SSD. With read/write speeds of up to 2,150MB/s and 1,550MB/s respectively, this NVMe PCIe SSD delivers much faster sustained performance than a SATA SSD.

While this shouldn’t make a significant difference to most CAD workflows, you should see a benefit when shifting large datasets around. The tiny M.2 form factor SSD sits flush on the motherboard. For additional storage, there are two front facing 3.5-inch drive bays. One of these is filled with an enterprise-class 4TB Western Digital HDD.