Sometimes our clients ask if they can use G-force GPUs rather than Quadro boards, even in multi-GPU external boxes, which is what some other post-production manufacturers are doing to reduce the costs. So we will dedicate a small technical white paper to explain the differences:
Question: Does G-force work with Mistika or do I need a Quadro?
Answer: Yes it works, but we recommend NVidia Quadro for a number of important reasons:
- Mistika is faster with Quadro: In general, when you have a post production application that can get the same performance with Quadro and G-force what it means is that this application is poorly optimised, or only partially based on GPU and can not get full advantage of a Quadro board. But that is not the case of Mistika:
A key aspect for Mistika realtime performance is not about the GPU processing but about the bus management. For example, when you need to move several layers of 4K images in realtime at high frame rates, it is usually the transfer of input and output images between the RAM and GPU what creates the ultimate performance limit, and not the GPU processing itself.
In a gaming application you only need to upload images to the GPU and then display those images directly in a computer monitor, but in a post-production system the results need to download to the SDI video board for playbacks, and also to the storage for the case of rendering. Also some complex effects, plugins and IO codecs, and decoding of complex formats like R3D also need several trips of the images between RAM and GPU and will be faster using a Quadro board rather than a Gforce model of similar specs.
And that is the main advantage of a Quadro board against a Gforce model, as the Quadro permits to move images in both directions at the same time. For example Mistika can be uploading the layers for the next frames, while processing the current frame and also downloading the finished images all at the same time. This is not possible in a Gforce.
The extra GPU memory in Quadro models is also important, as to do that we have to move extra images and keep multiple buffers where the realtime effects are running in the GPU.
Please note that as difference to other applications, the whole Mistika rendering engine is based on GPU, not only a small part of it as in other applications, so the extra memory provided by Quadro boards is also important
- Quadro can provide better quality: It is a surprising to see some manufacturers putting the "10 bit", "12 bit", or even "16 bit" labels everywhere in their marketing material as a quality seal, and then to see them selling their systems with G-force "gaming" boards. Gaming boards work at lower precision than Quadro in several aspects (for example truncating bits rather than rounding ...), and the quality can be degraded over the successive processing stages. This may not be significant if you plan to work with highly compressed formats (as they are not really precise anyway), but it can reduce the quality when working with high end cameras.
Also, all the tests in the SGO labs are made with Quadro boards, which is a warranty that any potential quality issues or image artifacts are detected and solved for Quadro boards, while they can pass unnoticed on other models.
- Quadro is more stable and robust: In a same way than a proper workstation is much more robust than a PC and can last for much longer. G-Force boards are designed for gaming, where stability is not a critical issue. Some of them can also be used as nice barbecues, but they are not really designed for client attended sessions.
Finally, SGO maintains a strong collaboration with NVidia to test at both sides and to make sure the Quadro drivers are free of bugs affecting the Mistika software.
However, there are still situations where you may want to use a Gforce model:
- When there are severe budget restrictions
- When upgrading very old systems, where a modern Quadro can not really deliver all its performance anyway. In these situations a Gforce can be a low cost option for a second life and extra performance.
- For generic render nodes not used for playbacks, except for very high end formats (ask support in case of doubt)
Question: What about external enclosures with several boards for mulitGPU support?
Answer: It may work, but in the case of Mistika it is not efficient.
The reason is the same as the first point. Applications that are only partially GPU optimised can benefit from this formula up to a certain point, just by using brute force. But when you have a software 100% GPU optimised like Mistika then the limiting factor is usually not the processing but the bus bandwidth. Typical external enclosures only use one PCIe slot, which put a hard limit when working in complex post production tasks. Instead, what we recommend for multiGPU is to install each GPU on its own dedicated slot, and always using the fastest model available first, rather than using several small units.
With this formula, Mistika Totem technology can send different frames to each GPU without any bandwidth interference, which is much more efficient than using SLI or external enclosures that need to share a common bus. For example, a Mistika system with two identical boards in two different slots can really render 200% faster in most situations (providing that there is enough disk speed to feed both of them)
Question: What GPU model is recommended for Mistika?
Answer: At the date of this document (April 2017) we specially recommend two models:
- NVidia Quadro P4000: For up to 4K and UHD workflows with effect stacks not too complex. Also excellent as a second GPU for background rendering, the P4000 is very cost effective.
- NVidia Quadro P6000: For high end performance, like 4K Stereo3D & 8K, and for complex production in general.