NVIDIA answers community questions
During a Q&A session on Reddit, NVIDIA employees have answered some of the most bothering questions from the subreddit community.
It is not a secret that the announcement of the Ampere RTX series did not provide too many details. In fact, it was limited to technology announcements, product design, and pricing.
Far more details were provided later, on NVIDIA and GeForce websites in blog posts and in official specifications.
The Q&A session did provide some answers directly from NVIDIA’s community managers. but we expect to learn a lot more after the press briefings planned for this week and after the first Ampere card is officially launched (September 17th).
HDMI 2.1 Specs
GhostMotley – Does Ampere support HDMI 2.1 with the full 48Gbps bandwidth
[Qi Lin] Yes. The NVIDIA Ampere Architecture supports the highest HDMI 2.1 link rate of 12Gbs/lane across all 4 lanes, and also supports Display Stream Compression (DSC) to be able to power up to 8K, 60Hz in HDR. [link]
SSD Requirement for Ampere
Pengwin17523 – Will there be a certain SSD speed requirement for RTX I/O?
[Tony Tamasi] There is no SSD speed requirement for RTX IO, but obviously, faster SSD’s such as the latest generation of Gen4 NVMe SSD’s will produce better results, meaning faster load times, and the ability for games to stream more data into the world dynamically. Some games may have minimum requirements for SSD performance in the future, but those would be determined by the game developers. RTX IO will accelerate SSD performance regardless of how fast it is, by reducing the CPU load required for I/O, and by enabling GPU-based decompression, allowing game assets to be stored in a compressed format and offloading potentially dozens of CPU cores from doing that work. Compression ratios are typically 2:1, so that would effectively amplify the read performance of any SSD by 2x. [link]
RTX IO
SBMS-A-Man108 – Does RTX IO allow use of SSD space as VRAM? Or am I completely misunderstanding?
[Tony Tamasi] RTX IO allows reading data from SSD’s at much higher speed than traditional methods, and allows the data to be stored and read in a compressed format by the GPU, for decompression and use by the GPU. It does not allow the SSD to replace frame buffer memory, but it allows the data from the SSD to get to the GPU, and GPU memory much faster, with much less CPU overhead. [link]
Aztec47 – Could we see RTX IO coming to machine learning libraries such as Pytorch? This would be great for performance in real-time applications
[Tony Tamasi] NVIDIA delivered high-speed I/O solutions for a variety of data analytics platforms roughly a year ago with NVIDIA GPU DirectStorage. It provides for high-speed I/O between the GPU and storage, specifically for AI and HPC type applications and workloads. For more information please check out: https://developer.nvidia.com/blog/gpudirect-storage/ [link]
Qrios1ty – I am excited for the RTX I/O feature but I partially don’t get how exactly it works?
[Tony Tamasi] RTX IO and DirectStorage will require applications to support those features by incorporating the new API’s. Microsoft is targeting a developer preview of DirectStorage for Windows for game developers next year, and NVIDIA RTX gamers will be able to take advantage of RTX IO enhanced games as soon as they become available.
NVIDIA Ampere Streaming Multiprocessor
redsunstar – With regards to the expected performance of the shaders units:
- Could you elaborate a little on these doubling of CUDA cores?
- How does it affect the general architectures of the GPCs?
- How much of a challenge is it to keep all those FP32 units fed?
- What was done to ensure high occupancy?
[Tony Tamasi] One of the key design goals for the Ampere 30-series SM was to achieve twice the throughput for FP32 operations compared to the Turing SM. To accomplish this goal, the Ampere SM includes new datapath designs for FP32 and INT32 operations. One datapath in each partition consists of 16 FP32 CUDA Cores capable of executing 16 FP32 operations per clock. Another datapath consists of both 16 FP32 CUDA Cores and 16 INT32 Cores. As a result of this new design, each Ampere SM partition is capable of executing either 32 FP32 operations per clock, or 16 FP32 and 16 INT32 operations per clock. All four SM partitions combined can execute 128 FP32 operations per clock, which is double the FP32 rate of the Turing SM, or 64 FP32 and 64 INT32 operations per clock.
Doubling the processing speed for FP32 improves performance for a number of common graphics and compute operations and algorithms. Modern shader workloads typically have a mixture of FP32 arithmetic instructions such as FFMA, floating point additions (FADD), or floating point multiplications (FMUL), combined with simpler instructions such as integer adds for addressing and fetching data, floating point compare, or min/max for processing results, etc. Performance gains will vary at the shader and application level depending on the mix of instructions. Ray tracing denoising shaders are good examples that might benefit greatly from doubling FP32 throughput.
Doubling math throughput required doubling the data paths supporting it, which is why the Ampere SM also doubled the shared memory and L1 cache performance for the SM. (128 bytes/clock per Ampere SM versus 64 bytes/clock in Turing). Total L1 bandwidth for GeForce RTX 3080 is 219 GB/sec versus 116 GB/sec for GeForce RTX 2080 Super.
Like prior NVIDIA GPUs, Ampere is composed of Graphics Processing Clusters (GPCs), Texture Processing Clusters (TPCs), Streaming Multiprocessors (SMs), Raster Operators (ROPS), and memory controllers.
The GPC is the dominant high-level hardware block with all of the key graphics processing units residing inside the GPC. Each GPC includes a dedicated Raster Engine, and now also includes two ROP partitions (each partition containing eight ROP units), which is a new feature for NVIDIA Ampere Architecture GA10x GPUs. More details on the NVIDIA Ampere architecture can be found in NVIDIA’s Ampere Architecture White Paper, which will be published in the coming days..
NVIDIA Ampere Streaming Multiprocessor according to HardwareLuxx vs NVIDIA Turing SM
For comparison, this is how NVIDIA introduced Turing Streaming Multiprocessor (SM):
Turing introduces a new processor architecture, the Turing SM, that delivers a dramatic boost in shading efficiency, achieving 50% improvement in delivered performance per CUDA Core compared to the Pascal generation. These improvements are enabled by two key architectural changes. First, the Turing SM adds a new independent integer datapath that can execute instructions concurrently with the floating-point math datapath. In previous generations, executing these instructions would have blocked floating-point instructions from issuing. Second, the SM memory path has been redesigned to unify shared memory, texture caching, and memory load caching into one unit. This translates to 2x more bandwidth and more than 2x more capacity available for L1 cache for common workloads.
PCI-Express 3.0 vs 4.0
Will PCIe 3.0 bottleneck the RTX 3090? Concerned because my Intel system does not support 4.0.
Tony Tamasi – System performance is impacted by many factors and the impact varies between applications. The impact is typically less than a few percent going from a x16 PCIE 4.0 to x16 PCIE 3.0. CPU selection often has a larger impact on performance.We look forward to new platforms that can fully take advantage of Gen4 capabilities for potential performance increases.
GeForce RTX 3070
tldrdoto – Please clarify if the slide saying RTX 3070 is equal or faster than 2080 Ti is referring to traditional rasterization or DLSS/RT workloads?
Very important if you could clear it up, since no traditional rasterization benchmarks were shown, only RT/DLSS supporting games.
[Justin Walker] We’re talking about both. Games that only support traditional rasterization and games that support RTX (RT+DLSS). You can see this in our launch article here https://www.nvidia.com/en-us/geforce/news/introducing-rtx-30-series-graphics-cards/ [link]
DLSS 2.1
EeK09 – What kind of advancements can we expect from DLSS? Most people were expecting a DLSS 3.0, or, at the very least, something like DLSS 2.1. Are you going to keep improving DLSS and offer support for more games while maintaining the same version?
[NV-Randy] DLSS SDK 2.1 is out and it includes three updates:
– New ultra performance mode for 8K gaming. Delivers 8K gaming on GeForce RTX 3090 with a new 9x scaling option.
– VR support. DLSS is now supported for VR titles.
– Dynamic resolution support. The input buffer can change dimensions from frame to frame while the output size remains fixed. If the rendering engine supports dynamic resolution, DLSS can be used to perform the required upscale to the display resolution. [link]
Power cables
Halogen19 – How bad would it be to run the 3080 off of a split connector instead of two separate cable. would it be potentially dangerous to the system if I’m not overclocking?
[NV_Tim] The recommendation is to run two individual cables. There’s a diagram here. https://www.nvidia.com/en-us/geforce/graphics-cards/30-series/rtx-3080/?nvmid=systemcomp
RTX Encoder
Carmen813 – Will there be any improvements to the RTX encoder in the Amphere series cards, similar to what we saw for the Turing Release? I did see info on the Broadcast software, but I’m thinking more along the lines of improvements in overall image quality at same bitrate.
[Jason Paul] for RTX 30 Series, we decided to focus improvements on the video decode side of things and added* AV1 decode support. On the encode side, RTX 30 Series has the same great encoder as our RTX 20 Series GPU. We have also recently updated our NVIDIA Encoder SDK. In the coming months, livestream applications will be updating to this new version of the SDK, unlocking new performance options for streamers.
NVIDIA Reflex
Akanash94 – Will Nvidia reflex work with pascal GPUs or is this only a Turing/Ampere feature?
[NV_Tim] It will work with 900 series + GPUs, including RTX 20-series.
Cooler design & airflow
iCinn – Any idea if the dual airflow design is going to be messed up for inverted cases? More than previous designs? Seems like it would blow it down on the CPU. But the CPU cooler would still blow it out the case. Maybe it’s not so bad.
Second question. 10x quieter than the Titan for the 3090 is more or less quieter than a 2080 Super (Evga ultra fx for example)?
[Qi Lin] u/iCinn The new flow through cooling design will work great as long as chassis fans are configured to bring fresh air to the GPU, and then move the air that flows through the GPU out of the chassis. It does not matter if the chassis is inverted.
The Founders Edition RTX 3090 is quieter than both the Titan RTX and the Founders Edition RTX 2080 Super. We haven’t tested it against specific partner designs, but I think you’ll be impressed with what you hear… or rather, don’t hear. :-)
Source: Reddit, HardwareLuxx
