FPGA hardware acceleration is an approach to offload tasks in computer-aided engineering environments. FPGA hardware acceleration enhances the performance and speed of system operation.
The basic building blocks of FPGAs are Configurable Logic Blocks ❲CLBs❳ and Programmable Interconnects ❲PIs❳.
The general strategy of FPGA hardware acceleration includes the following steps- design, synthesis, implementation, and bitstream generation.
Figure1: FPGA board
As engineering problems become increasingly complicated, it can be difficult to deliver computer-aided solutions without errors. Even after several rounds of analysis and testing, some glitches in a solution may remain unnoticed and later get revived in real-work sites to collapse the system. Nowadays the heterogeneous application of computers and embedded systems demand that troubleshooting is carried out after programming or fabrication. A customized version of a processing system, generally called computer hardware, is the current trend for enhancing system performance and flexibility.
Field Programmable Gate Array (FPGA) is a well-known reconfigurable computer hardware device that is widely applied in various engineering fields. Compared to software running on generic processors, FPGAs are found to be more productive and efficient when executing applications with specified functions. Any set of instructions from a given application can either run on software installed on a computer or on an FPGA.
The parallel computing feature keeps FPGAs distinctive from generic processing units. Engineering applications involving computational tasks utilize the FPGA hardware acceleration approach to improve the performance and speed of operation. A reduction in power consumption, decreased latency, and wide bandwidth operation are a few other advantages of FPGAs.
FPGA Hardware Acceleration
FPGA hardware acceleration assures offloading of certain computational tasks within an application platform and gains higher efficiency than running the same tasks on a generic processor. It is somewhat similar to activity migration in MPSoC. Instead of transferring tasks to the cores, in FPGA hardware acceleration, the activity gets migrated or offloaded to an FPGA. The offloaded tasks run at FPGA clock speed and improve the performance and runtime of the entire system.
FPGAs are programmed depending on the ‘field’ of application and perform the assigned task precisely. Compared to Application-Specific ICs ❲ASIC❳, FPGAs can be reconfigured at any point of time and there will be no trace of the previous instructions left. This enables the use of the same FPGA board for different purposes.
Merits of FPGA Hardware Acceleration
Compared to high-end processors and ASICs, the clock speed of FPGAs is low. With this limitation, there is also a loud shout-out for FPGA hardware acceleration from hardware engineers. The configurable features are the most appealing factor of FPGAs, followed by reduced power consumption and performance. Few other notable merits of FPGA hardware acceleration are:
Increased parallelism- Multiple tasks from a single application can be run simultaneously. Demanding computational tasks can be solved without consuming much time by incorporating FPGA boards for task migration.
Expandable size of data- In FPGAs, the number of bits in the operands in an arithmetic operation can be changed based on requirements. This expansion of the bit size allows any change in the data amidst programming.
Suitability for prototyping and validation- The reconfiguration property of FPGAs are well-utilized for prototyping ASICs and SoCs, as they get permanently configured once fabricated. The FPGA prototype is built and validated before starting ASIC fabrication.
The dynamic reconfiguration possibility in FPGA has increased its utilization in electronics, communication, automobile, and aerospace environments. The recent FPGA technology releases incorporate processor cores, artificial intelligence processing units, and Digital Signal Processing ❲DSP❳ chips as a move to transfer a good share of workloads onto FPGA boards. The optimized-FPGAs are becoming more energy-efficient, with increased speed and memory. The influence of customizable computer hardware is growing tremendously, and in-depth knowledge of FPGA boards will help you to design and implement FPGA hardware accelerators.
A Glimpse at FPGA Architecture
Figure 2: Schematic of FPGA architecture
FPGAs integrate flexibility, speed, versatility, performance, and efficiency into a printed circuit board, and calls for the offloading of complex tasks in a system to it. FPGAs are programmed for specific applications. Usually, computer languages such as Verilog or VHDL are used for writing the code. The instruction codes in these Hardware Descriptive Languages (HDLs) are capable of bringing logic changes in the FPGA internal circuitry, thus accomplishing task completion.
The basic building blocks of FPGAs are configurable logic blocks ❲CLBs❳, and the distributed interconnects called programmable interconnects ❲PIs❳. The CLBs are composed of flip-flops, multiplexers, look-up-tables ❲LUTs❳, and supplementary logic. FPGAs come with two types of memory: embedded and distributed. Embedded memory forms the block RAM and offers data storage space and buffering. Distributed memory can be ROM or RAM. These memory blocks are constructed using LUTs. Apart from these blocks, FPGAs contain other components such as DSP chips, PLLs, and external memory controllers.
In the FPGA hardware acceleration process, logic blocks and interconnects get configured and reconfigured according to the program which enables a relevant chip present in FPGA for the execution of assigned tasks. A schematic of the FPGA architecture is given in Figure 2 (above).
General Strategy of FPGA Hardware Acceleration
The general strategy of FPGA hardware acceleration is comprised of four steps:
Design- The system to be implemented using FPGA should be modeled either using HDL or schematic. The architecture modeled in HDL can be converted into schematic and vice-versa. The schematic is modeled using blocks based on sources such as VHDL specification, user-defined library blocks, and system Intellectual Property ❲IP❳ cores. The three sources are integrated either using structural HDL code or IP integrator. The schematic approach improves the visibility of the system, however, it is suitable only for systems with low complexity. For complex systems, VHDL or Verilog language approaches seem more appropriate.
Synthesis-After design, the synthesis is carried out in a software-based design environment. The entire system model is developed with logic gates, flip-flops, and multipliers in the synthesis step, and a netlist gives the interconnection between each of these components. A mapping process is carried out to connect the design to logic and the associated time is also estimated.
Implementation- The synthesized netlist is transferred to the FPGA during the implementation process. The constraints and netlists are gathered. The constraints define the input-output pins of FPGAs and also initialize the input clock. This phase acknowledges the resources in the design files and those given to the FPGA.
Bitstream generation-In this step, the architecture which is synthesized and implemented in previous steps is converted into the bitstream. The bitstream generated is loaded into the FPGA. Now, your FPGA is operating as a hardware accelerator.
FPGA hardware acceleration enhances the speed of system operation and general performance. Through four simple steps outlined above (design, synthesis, implementation, and bitstream generation), you can enhance your project with FPGA hardware acceleration, ensuring a productive and efficient execution of applications.