DNA of a Modern Mid-Range FPGA

While it is tempting to classify FPGAs simply based on logic capacity, modern FPGAs are alterable systems on chips with a wide variety of features and resources. In this blog we look closer at requirements of the mid-range segment of the FPGA industry.

Altera was the first company to release a dedicated mid-range family of devices. From its inception, the Arria family has always been about striking the right balance between performance, power and cost-effectiveness. Filling the space between cost-optimized devices like Cyclone and high-performance devices like Stratix. The key to this balance is providing high-performance and advanced features with a moderate sized fabric and the right peripherals for an economical solution. Let’s take a closer look at what makes up a mid-range FPGA.

High Performance Fabric

Logic capacity is only one metric for an FPGA fabric. The vast majority of applications that require the densities of a mid-range device, also need logic to run at speeds sufficient to keep up with high-speed transceivers and modern memory interfaces. This level of performance is simply not achievable with the basic 4-input LUT because complex logic requires too many layers which limits the operating frequency. A 6-input LUT is the minimum needed to meet mid-range performance levels, and a more advanced logic block like Altera’s 8-input Adaptive Logic Module is ideal. (Learn more about the advantages of the Altera ALM HERE.)

Hard IP / Memory Controllers

Another important element in mid-range FPGAs is hard IP, especially memory controllers. Many applications require external memory, and it is important to make use of modern memory interfaces to get the data in and out of the device with a manageable number of pins. Implementing interfaces like these to operate at speed in a programmable device is not trivial. Since this is such a common IP to be used in these applications and because the memory interfaces are standardized, providing hardened blocks to implement these functions is optimal. The hardened blocks are guaranteed to meet timing and consume much less die area than when implemented in the fabric. The same applies to other common IP blocks such as PCIe or ethernet controllers.

High Speed Transceivers

Like memory interfaces, high-speed transceivers are another key feature in a mid-range FPGA. Fast pipes are needed to feed data to the logic and memory. FPGAs are very versatile and used in many applications, so these transceivers need to be equally versatile. It is important to choose a device with flexible transceivers and a company with a vast IP library to cover the standards that you require. As transceiver speeds increase, the signal integrity issues become more challenging and advanced tools like the Quartus Prime Transceiver Toolkit become indispensable for development. Always include the transceiver tools and IP libraries in your mid-range FPGA evaluation.

Partial Reconfiguration

One of the biggest advantages of an FPGA is the ability to change the behavior on the fly as needed. This ability can be used to fix a bug, adapt to a changing standard, add a new feature, and to improve time to market. In some cases, it is important to apply an update without taking down the system, which may depend on some of the logic inside the FPGA. Partial reconfiguration makes this possible. Partial reconfiguration can also help fit into a smaller device (or add a feature without growing to a larger device) because you may be able to time share logic by swapping it out on the fly.

Hard Processor Subsystem

Nearly every electronic device today includes some form of processor. Every programmable logic device likely has a processor inside it or next to it. A leading FPGA provider will offer a suite of embedded processors to choose from including both soft and hardened processors. Integrated processors in FPGAs have significant advantages saving power and pins when sharing data between the processor and logic. Like any common IP block, a hardened processor will be much faster and more efficient in power and silicon area than one implemented in logic. In the past, integrated processors provided limited performance compared to discrete embedded processors, but the integrated processors in newer mid-range devices like Agilex 5 rival many industrial embedded processors. When choosing a mid-range FPGA, ensure there are options with integrated hard processors.

Summary

Mid-range FPGAs are more than a class defined by logic capacity. A true mid-range FPGA is optimized to provide cost-effective performance through a combination of high-performance fabric, hard memory controllers, high-speed transceivers, partial reconfiguration, and hard processor subsystems. Finally, we must remember that not all applications require a mid-range device. Be sure to work with an FPGA company that offers the complete spectrum of FPGAs from top to bottom, so that you do not need to change tools or ecosystems for simpler applications, or when your needs outgrow a mid-range FPGA