computer science

Qualcomm Hexagon

Qualcomm Hexagon is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Qualcomm Hexagon rather than just read about it. In short: Hexagon is the brand name for a family of digital signal processor (DSP) and later neural processing unit (NPU) products by Qualcomm. Hexagon is also known as QDSP6, standing for “sixth generation digital signal processor.” According to Qualcomm, the Hexagon architecture is designed to deliver performance with low power over a variety of applications.

Key takeaways

Qualcomm Hexagon belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Qualcomm Hexagon to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Qualcomm Hexagon from memory before moving on to harder problems.

Reference excerpt

Hexagon is the brand name for a family of digital signal processor (DSP) and later neural processing unit (NPU) products by Qualcomm. Hexagon is also known as QDSP6, standing for “sixth generation digital signal processor.” According to Qualcomm, the Hexagon architecture is designed to deliver performance with low power over a variety of applications. Each version of Hexagon has an instruction set and a micro-architecture. These two features are intimately related. Hexagon is used in Qualcomm Snapdragon chips, for example in smartphones, cars, wearable devices and other mobile devices and is also used in components of cellular phone networks.

Instruction set architecture Computing devices have instruction sets, which are their lowest, most primitive languages. Common instructions are those which cause two numbers to be added, multiplied or combined in other ways, as well as instructions that direct the processor where to look in memory for its next instruction. There are many other types of instructions. Assemblers and compilers that translate computer programs into streams of instructions – bit streams - that the device can understand and carry out (execute). As an instruction stream executes, the integrity of system function is supported by the use of instruction privilege levels. Privileged instructions have access to more resources in the device, including memory. Hexagon supports privilege levels. Originally, Hexagon instructions operated on integer numbers but not floating point numbers, but in v5 floating point support was added. The processing unit which handles execution of instructions is capable of in-order dispatching up to 4 instructions (the packet) to 4 execution units every clock.

Micro-architecture Micro-architecture is the physical structure of a chip or chip component that makes it possible for a device to carry out the instructions. A given instruction set can be implemented by a variety of micro-architectures. The buses – data transfer channels – for Hexagon devices are 32 bits wide. That is, 32 bits of data can be moved from one part of the chip to another in a single step. The Hexagon micro-architecture is multi-threaded, which means that it can simultaneously process more than one stream of instructions, enhancing data processing speed. Hexagon supports very long instruction words, which are groupings of four instructions that can be executed “in parallel.” Parallel execution means that multiple instructions can run simultaneously without one instruction having to complete before the next one starts. The Hexagon micro-architecture supports single instruction, multiple data operations, which means that when a Hexagon device receives an instruction, it can carry out the operation on more than one piece of data at the same time. According to 2012 estimation, Qualcomm shipped 1.2 billion DSP cores inside its system on a chip (SoCs) (average 2.3 DSP core per SoC) in 2011, and 1.5 billion cores were planned for 2012, making the QDSP6 the most shipped architecture of DSP (CEVA had around 1 billion of DSP cores shipped in 2011 with 90% of IP-licensable DSP market). The Hexagon architecture is designed to deliver performance with low power over a variety of applications. It has features such as hardware assisted multithreading, privilege levels, very long instruction word (VLIW), single instruction, multiple data (SIMD), and instructions geared toward efficient signal processing. Hardware multithreading is implemented as barrel temporal multithreading - threads are switched in round-robin fashion each cycle, so the 600 MHz physical core is presented as three logical 200 MHz cores before V5. Hexagon V5 switched to dynamic multithreading (DMT) with thread switch on L2 misses, interrupt waiting or on special instructions. At Hot Chips 2013 Qualcomm announced details of their Hexagon 680 DSP. Qualcomm announced Hexagon Vector Extensions (HVX). HVX is designed to allow significant compute workloads for advanced imaging and computer vision to be processed on the DSP instead of the CPU. In March 2015 Qualcomm announced their Snapdragon Neural Processing Engine SDK which allow AI acceleration using the CPU, GPU and Hexagon DSP. Qualcomm's Snapdragon 855 contains their 4th generation on-device AI engine, which includes the Hexagon 690 DSP and Hexagon Tensor Accelerator (HTA) for AI acceleration. Snapdragon 865 contains the 5th generation on-device AI engine based on the Hexagon 698 DSP capable of 15 trillion operations per second (TOPS). Snapdragon 888 contains the 6th generation on-device AI engine based on the Hexagon 780 DSP capable of 26 TOPS. Snapdragon 8 contains the 7th generation on-device AI engine based on the Hexagon DSP capable of 52 TOPS and up to 104 TOPS in some cases.

Software support

Operating systems The port of Linux for Hexagon runs under a hypervisor layer ("Hexagon Virtual Machine") and was merged with the 3.2 release of the kernel. The original hypervisor is closed-source, and in April 2013 a minimal open-source hypervisor implementation for QDSP6 V2 and V3, the "Hexagon MiniVM" was released by Qualcomm under a BSD-style license.

Compilers Support for Hexagon was added in 3.1 release of LLVM by Tony Linthicum. Hexagon/HVX V66 ISA support was added in 8.0.0 release of LLVM. There is also a non-FSF maintained branch of GCC and binutils.

Adoption of the SIP block Qualcomm Hexagon DSPs have been available in Qualcomm Snapdragon SoC since 2006. In Snapdragon S4 (MSM8960 and newer) there are three QDSP cores, two in the Modem subsystem and one Hexagon core in the Multimedia subsystem. Modem cores are programmed by Qualcomm only, and only Multimedia core is allowed to be programmed by user. They are also used in some femtocell processors of Qualcomm, including FSM98xx, FSM99xx and FSM90xx.

Third-party integration In March 2016, it was announced that semiconductor company Conexant's AudioSmart audio processing software was being integrated into Qualcomm's Hexagon. In May 2018 wolfSSL added support for using Qualcomm Hexagon. This is support for running wolfSSL crypto operations on the DSP. In addition to use of crypto operations a specialized operation load management library was later added.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Qualcomm Hexagon

Start with the simplest possible case. Write down what Qualcomm Hexagon claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Qualcomm Hexagon before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Qualcomm Hexagon ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Qualcomm Hexagon

In research: Qualcomm Hexagon appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Qualcomm Hexagon in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Qualcomm Hexagon is common in secondary-school and first-year university syllabi. It links to neighbouring topics Digital signal processors, Neural processing units, Qualcomm IP cores, so understanding it makes those chapters shorter.
In everyday life: Look for Qualcomm Hexagon outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Qualcomm Hexagon in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Qualcomm Hexagon means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Qualcomm Hexagon out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Qualcomm Hexagon in simple terms?

Why does Qualcomm Hexagon matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Qualcomm Hexagon?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Qualcomm Hexagon.