For ARM, MCU, DSP, FPGA, and SoC, everyone is likely familiar, but are you sure you really understand them? Do you know the connections and differences between these five? Don’t worry, let’s explore it right away!
ARM
The ARM processor is the first RISC microprocessor designed by Acorn Computers Ltd. for the low-budget market, originally known as the Acorn RISC Machine. The ARM processor is inherently a 32-bit design but also includes a 16-bit instruction set, generally saving up to 35% compared to equivalent 32-bit code while retaining all the advantages of a 32-bit system.
History of ARM:
On December 5, 1978, physicist Hermann Hauser and engineer Chris Curry founded the CPU Company (Cambridge Processing Unit) in Cambridge, England, primarily to supply electronic devices to the local market. In 1979, the CPU Company was renamed Acorn Computers Ltd.
Initially, Acorn intended to use Motorola’s 16-bit chips but found them too slow and expensive. “A machine priced at £500 cannot use a £100 CPU!” They turned to Intel for the design of the 80286 chip but were refused, forcing them to develop their own.
In 1985, Roger Wilson and Steve Furber designed their first generation 32-bit, 6 MHz processor, which they used to create a RISC instruction set computer, abbreviated as ARM (Acorn RISC Machine). This is where the name ARM comes from.
RISC stands for “Reduced Instruction Set Computer,” which supports simpler instructions, resulting in lower power consumption and cost, making it particularly suitable for mobile devices. A typical early device using ARM chips was Apple’s Newton PDA.
By the late 1980s, ARM quickly developed into Acorn’s desktop products, forming the foundation of computer education in the UK.
On November 27, 1990, Acorn officially restructured into ARM Holdings. Apple invested £1.5 million, chip manufacturer VLSI contributed £250,000, and Acorn itself invested £1.5 million in intellectual property and 12 engineers. The company’s office was very modest, just a barn. In the 1990s, ARM’s 32-bit embedded RISC processors expanded globally, leading the field of low-power, low-cost, and high-performance embedded system applications. ARM does not manufacture or sell chips; it only licenses chip technology.
MCU
An MCU is essentially a microcontroller, which integrates the CPU, RAM, ROM, timer/counter, and various I/O interfaces onto a single chip, forming a chip-level computer.
Leading MCU manufacturers include Renesas, NXP, Nuvoton, Microchip, STMicroelectronics, Atmel, Infineon, Texas Instruments, Toshiba, Samsung, Cypress, Analog Devices, Qualcomm, Fujitsu, AMD, Holtek, and many others.
DSP
DSP (Digital Signal Processing) refers to the theory and technology of processing signals using numerical calculations. DSP also stands for Digital Signal Processor, which is a chip that integrates a dedicated computer, about the size of a coin.
FPGA
FPGA (Field-Programmable Gate Array) is a product developed further from programmable devices like PAL, GAL, and CPLD. It appears as a semi-custom circuit in the ASIC domain, addressing the shortcomings of custom circuits while overcoming the limitations of programmable devices with a limited number of gates.
Leading FPGA manufacturers include Altera (acquired by Intel), Xilinx, Actel, Lattice, Atmel, QuickLogic, Microsemi, Cypress, TI, and many others.
SoC
SoC has various definitions due to its rich connotation and wide application range, making it difficult to provide an exact definition. Generally, SoC refers to a system-on-chip, meaning it is a product, an integrated circuit with a specific purpose, containing a complete system and all embedded software. It is also a technology that implements the entire process from defining system functions to hardware/software partitioning and completing the design.
Comparison of ARM, MCU, DSP, FPGA, and SoC
1Architecture
ARM: The architecture uses a 32-bit RISC processor architecture. Starting from ARM9, ARM adopted the Harvard architecture, which separates instructions and data into their respective memory structures, significantly improving processing capability. ARM often employs pipelining technology, which shortens program execution time by allowing multiple power components to work in parallel, enabling instructions to flow through multiple pipelines, thus enhancing processor efficiency and throughput. Currently, ARM7 uses a typical three-stage pipeline, ARM9 uses a five-stage pipeline, ARM11 uses a seven-stage pipeline, and ARM Cortex-A9 even employs a variable pipeline structure (supporting 8-11 stages). The ARM Cortex-A9 supports up to four cores, marking the first time multi-core technology is supported in the ARM series processors. The following diagram shows the internal structure of ARM Cortex-A9.
MCU: Most are based on the von Neumann architecture, which clearly defines the four essential components of embedded systems: a central processing unit core, program memory (ROM or flash), data memory (RAM), one or more timers/counters, and input/output ports for communication with peripheral devices and extended resources—all integrated into a single integrated circuit chip. Early MCUs used CISC instruction sets, later replaced by RISC. In terms of bus width, MCUs cover 4-bit, 8-bit, 16-bit, and 32-bit, with widespread applications.
DSP: Also known as digital signal processors, these are microprocessors specifically designed for real-time digital signal processing. Structurally, they adopt the Harvard architecture and also use pipelining technology. Additionally, DSPs can operate as direct memory access devices in host environments and support data acquisition from analog-to-digital converters (ADC), ultimately outputting data converted to analog signals by digital-to-analog converters (DAC), supporting a certain level of parallel processing.
FPGA: FPGA stands for Field Programmable Gate Array, which is a product developed further from programmable devices like PAL, GAL, and PLD, and is the highest integrated form of ASIC. FPGA employs a new concept called Logic Cell Array (LCA), which includes configurable logic blocks (CLB), input/output blocks (IOB), and interconnects. Users can reconfigure the internal logic and I/O modules of the FPGA to implement their logic. It also features static reprogrammability and dynamic in-system reconfiguration, allowing hardware functions to be modified through programming like software. The main difference between FPGA and DSP, ARM, and MCU lies in its parallel processing capability, which significantly enhances the speed of complex calculations.
SoC: A system-on-chip integrates a computer or other electronic systems into a single chip. SoCs can process digital signals, analog signals, mixed signals, and even higher frequency signals. SoCs are often used in embedded systems. The integration scale of SoCs is large, typically reaching millions to tens of millions of gates. SoCs are relatively flexible, allowing the integration of ARM architecture processors with dedicated peripheral chips to form a system. Some ARM processors, such as Hisi-3507 and Hisi-3516, are SoC systems, especially application processors that integrate many peripheral devices, providing strong support for executing more complex tasks and applications.
2Power Consumption
ARM: It can be said that the main reason for ARM’s great success in the mobile market is its low power consumption. It is well known that electronic products in the mobile market are very sensitive to processor power consumption. In the past, processor power consumption on PC platforms ranged from tens to hundreds of watts, which is unimaginable for mobile platforms. ARM operates at a frequency of 1 GHz with a power consumption of only a few hundred mW, making it suitable for mobile electronic products.
DSP: According to a set of data from Non-Volatile, DSP and FPGA each hold half of the market share in digital signal processing. One advantage of DSP over FPGA is its relatively low power consumption. DSP manufacturers ensure their market share by increasing processor frequency and striving to reduce power consumption, as FPGA seems to have an advantage in high-performance digital processing markets. In the DSP field, TI’s DSP processors are known for their lower cost and power consumption compared to other DSP manufacturers, making TI’s DSP chips more competitive.
MCU: MCUs have been around the longest, with various manufacturers having their own architectures and instruction sets. In terms of low power consumption, TI’s MSP430 MCU performs relatively well.
FPGA: Due to its internal structure, FPGA has relatively high power consumption and generates significant heat, which is a drawback. However, this is unavoidable, as it supports high-performance concurrent computing digital circuits, and the internal logic gates mostly use standard width-to-length ratios, resulting in power consumption that cannot compare with ASICs and other dedicated processors.
SoC: Due to the flexibility of SoCs, which integrate multiple devices into a very small chip to form a system, SoC systems have an advantage in power consumption compared to systems composed of MCUs and other processors. Additionally, SoC chips can optimize system power consumption at the layout level by combining process, circuit design, and other factors, resulting in lower power consumption and smaller footprint compared to systems built with current peripheral PCBs.
3Speed
As market application demands increase, ARM manufacturers are optimizing to enhance their clock frequency and performance. From an initial 100 MHz to an astonishing 2.3 GHz, ARM’s clock frequency has advanced rapidly.
The fastest current DSP can reach a clock frequency of 1.2 GHz. However, it is not appropriate to judge performance solely based on clock frequency; DSPs can complete one multiplication and one addition in a single clock cycle, a capability that general ARM processors typically lack. DSPs have a clear advantage in computational fields, so TI has combined the strengths of both ARM and DSP to produce the DaVinci heterogeneous chip, which falls under the SoC category.
MCUs, as low-end application processors, have clock frequencies ranging from several MHz to tens of MHz.
FPGAs can achieve clock frequencies of several GHz, even exceeding 10 GHz, although they come at a high cost. Comparing FPGA with ARM, DSP, etc., based on clock frequency is not very meaningful, as the parallel computing capability far exceeds that of general-purpose processors using serial computation by dozens of times. For example, implementing the same filtering algorithm on a 100 MHz FPGA is still faster than on a 1 GHz ARM.
4Applications and Market
ARM processors are currently divided into three series: A series, R series, and M series, with the A series primarily targeting consumer electronics applications and being widely used.
Computing: netbooks, smartbooks, input boards, e-book readers, thin clients
Mobile: smartphones, feature phones
Digital Appliances: set-top boxes, digital TVs, Blu-ray players, game consoles
Automotive: infotainment, navigation
Enterprise: laser printers, routers, wireless base stations, VOIP phones and devices
Wireless Infrastructure: Web 2.0, wireless base stations, switches, servers
The R series processors mainly target applications with high real-time requirements, such as aerospace and automotive electronics, featuring high reliability, high availability, high fault tolerance, and real-time response.
The M series processors primarily target lower-end applications, with the initial goal of replacing existing MCUs on the market.
ARM Cortex-M0
ARM Cortex-M0+
ARM Cortex-M3
ARM Cortex-M4
“8/16-bit” applications
“8/16-bit” applications
“16/32-bit” applications
“32-bit/DSC” applications
Low cost and simplicity
Low cost, optimal energy efficiency
High performance, general-purpose
Effective digital signal control
DSP primarily targets applications requiring high computational power, such as video image processing, intelligent robotics, digital wireless, broadband access, digital audio, high-resolution imaging, and digital motor control.
MCUs are the most widely used, primarily benefiting from cost control, allowing them to establish a foothold in many applications that do not require high computational power. It is believed that in the coming years, the key growth drivers for the MCU market will come from green energy, smart electronic devices, smart grids, and upgrades of electronic products such as automotive electronics.
SoC applications are also very widespread, mainly because the existing mainstream ARM chips adopt architectures that are a type of SoC. SoC is a broad concept, and many ARM and DSPs are beginning to adopt SoC methods to integrate multiple devices onto processors to form complex systems.
5Development Costs
ARM primarily runs on operating systems like LINUX, ANDROID, and WINCE, and in terms of development difficulty, it is relatively more challenging than MCUs and DSPs, requiring developers to have a deep understanding of operating systems; in terms of cost, the single-chip cost of ARM is higher than that of MCUs, mainly used in more complex systems.
MCUs are the easiest to get started with, quick to learn, and have low development difficulty, making them widely used in low-end markets.
DSPs are relatively easy to start with, but their single-chip costs are higher, mainly used in applications requiring high computational power. Of course, DSPs can also run operating systems, making them suitable for multitasking applications.
FPGA development is relatively difficult and has a longer development cycle, and its single-chip cost is also high.
Generally, performing such an operation requires 9 multiplications and 8 additions, which is quite easy on FPGAs and DSPs, but for ARM and MCUs, their parallel capabilities are not strong, making them struggle when processing larger images, such as 1280P.
However, such operations can be easily optimized. For example, the pixel points at positions 1 and -1 can be completed with a single addition, and similarly, the last row can be done the same way. The corresponding pixel points of 2 and -2 in the middle row can also be added once and then shifted to complete the operation. The calculation is reduced from 9 multiplications and 8 additions to three additions and one shift (the shift operation can generally be completed in a single clock cycle on most processors).
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