Formalizing Nvidia Ampere

A structured way to describe a complex computing engine

BNF serves as a robust framework for developers to comprehend the intricate design of Nvidia’s Ampere microarchitecture efficiently.

The Backus-Naur Form (BNF) is a valuable tool for understanding computer architectures because it concisely defines complex systems using hierarchical structures and clear, formal syntax.

By breaking down the architecture into fundamental components such as processing units, memory, interconnects, software support, and specialized features, BNF facilitates a structured and modular representation. This enables a clear visualization of the relationships and dependencies between different elements of the microarchitecture.

For instance, using BNF to specify the number of CUDA cores, Tensor Cores, and the clock speeds provides a clear snapshot of the processing capabilities. Similarly, detailing memory types, capacities, and bandwidths helps in understanding the data handling and storage aspects.

The formalism of BNF also makes it easier to identify key characteristics and compare different architectural generations.

BNF Use Case: Nvidia’s Ampere

Here’s a BNF specification for Nvidia’s Ampere architecture,

<Ampere_Architecture> ::= <Architecture_Name> <Processor> <Memory> <Interconnect> <Software_Support> <Features>

<Architecture_Name> ::= "Ampere"

<Processor> ::= <SM_Count> <Core_Count> <Clock_Speeds> <Tensor_Cores> <RT_Cores>
<SM_Count> ::= "SM Count" "108"
<Core_Count> ::= "CUDA Cores" "6912"
<Clock_Speeds> ::= <Base_Clock> <Boost_Clock>
<Base_Clock> ::= "Base Clock" "1410 MHz"
<Boost_Clock> ::= "Boost Clock" "1730 MHz"
<Tensor_Cores> ::= "Tensor Cores" "432"
<RT_Cores> ::= "Ray Tracing Cores" "84"

<Memory> ::= <Memory_Type> <Memory_Capacity> <Memory_Bandwidth>
<Memory_Type> ::= "HBM2" | "HBM2e"
<Memory_Capacity> ::= "40 GB" | "80 GB"
<Memory_Bandwidth> ::= "1555 GB/s" | "2039 GB/s"

<Interconnect> ::= <NVLink> | <PCIe>
<NVLink> ::= "NVLink" "600 GB/s"
<PCIe> ::= "PCIe" <Version> <Lane_Count>
<Version> ::= "Gen4"
<Lane_Count> ::= "16"

<Software_Support> ::= <CUDA> <TensorRT> <NCCL>
<CUDA> ::= "CUDA" "11.0"
<TensorRT> ::= "TensorRT" "7.2"
<NCCL> ::= "NCCL" "2.7"

<Features> ::= <Special_Features>
<Special_Features> ::= <Feature> | <Feature> <Special_Features>
<Feature> ::= "Multi-Instance GPU" | "NVSwitch" | "DLSS" | "Third-Gen Tensor Cores" | "Second-Gen Ray Tracing Cores"

<Number> ::= "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" | <Number> <Number>

Explanation:

  • Architecture_Name: Specifies the architecture name, which is “Ampere”.
  • Processor: Describes the processing units with numerical values for Streaming Multiprocessor (SM) count, CUDA core count, base and boost clock speeds, Tensor Cores, and Ray Tracing Cores.
  • Memory: Defines the memory type, capacity, and bandwidth with numerical values.
  • Interconnect: Details the interconnection standards with specific values for NVLink speed and PCIe version and lanes.
  • Software_Support: Lists the software frameworks and their specific versions compatible with the Ampere architecture.
  • Features: Includes specialized features such as Multi-Instance GPU (MIG) technology, NVSwitch, DLSS, and generations of Tensor and Ray Tracing Cores.
  • Number: Terminals for representing numerical values.

What’s a CUDA Core?

A CUDA (Compute Unified Device Architecture) core is a processing unit within the GPU that executes parallel computations. Each CUDA core is designed to handle a single floating-point or integer operation per clock cycle. The core architecture is optimized for massively parallel computations, making it ideal for tasks such as scientific simulations, deep learning, image processing, and other compute-intensive applications.

If we consider matrix multiplication as a practical example, each CUDA core can handle an element of the matrix multiplication independently. Given matrices \( A \) and \( B \), the product \( C = A \times B \) can be computed where each element \( c_{ij} \) is the dot product of the \( i \)-th row of \( A \) and the \( j \)-th column of \( B \). With CUDA cores, these computations for each \( c_{ij} \) can be performed in parallel, drastically reducing computation time.

HBM2 (High Bandwidth Memory 2) is a type of computer memory designed for high-performance GPUs and other computing devices. It stacks memory chips vertically and connects them with a fast interface, allowing for much higher data transfer speeds and more memory in a smaller space compared to traditional memory types like GDDR6. This design helps GPUs handle large amounts of data quickly, improving performance for tasks like AI, and scientific computations.

HBM2e (High Bandwidth Memory 2 Enhanced) is an improved version of HBM2. It offers even higher data transfer speeds and larger capacity, allowing for even better performance in demanding applications. HBM2e maintains the same stacked design and fast interface but pushes the boundaries further, enabling GPUs to process more data faster, which is crucial for advanced computing tasks like deep learning and complex simulations.

NVLink is a high-speed connection technology developed by Nvidia that allows GPUs to communicate with each other and with CPUs much faster than traditional methods like PCIe. By creating a direct, high-bandwidth link between multiple GPUs or between a GPU and a CPU, NVLink enables faster data transfer and more efficient parallel processing. This boosts the performance of applications that need to handle large amounts of data quickly, such as AI training, scientific computing, and complex simulations.