IP Cores: Sources, Licensing, and Implementation in Semiconductor Design
In the complex world of semiconductor manufacturing, creating a chip from scratch is an immense undertaking. To accelerate development and reduce risk, engineers rely on IP cores—pre-designed, reusable functional blocks of logic. These cores act as the building blocks of modern integrated circuits, allowing companies to integrate complex functionality without reinventing the wheel.
Key Facts
- Silicon IP (SIP) is a business model where technology is licensed as intellectual property rather than sold as physical chips.
- Soft cores are programmable and flexible, while hard cores are pre-implemented for specific manufacturing processes.
- RISC (Reduced Instruction Set Computer) architectures are preferred over CISC (Complex Instruction Set Computer) for embedded systems due to smaller logic requirements.
- IP hardening converts flexible RTL designs into verified hardware layouts (GDSII) that meet foundry manufacturing rules.
- Open-source initiatives like RISC-V and OpenCores.org provide free alternatives to proprietary licensed IP.
Licensed Functionality
Licensed IP cores cover a vast spectrum of chip functionality, ranging from the central processing unit to specialized peripheral controllers.
Microprocessor Designs
Many of the most prominent IP cores are soft microprocessor designs. These vary in scale from small 8-bit processors, such as the 8051 and PIC, to powerful 32-bit and 64-bit architectures like ARM and RISC-V. These processors serve as the "brains" of embedded systems. Most utilize RISC instruction sets because they require less logic than CISC sets (such as x86), resulting in smaller designs. Notably, x86 leaders Intel and AMD protect their intellectual property heavily and do not follow this licensing model for their x86-64 lines.
Peripheral and Fixed-Function Controllers
Beyond processors, IP is licensed for peripheral controllers including USB, Ethernet, PCI Express, SDRAM, LCD, AGP, IEEE 1394, and AC'97 audio. Many of these interfaces require a combination of digital logic and analog IP cores to manage high-voltage, high-speed, or high-impedance signals that leave the chip.
Additionally, "hardwired" digital logic cores are licensed for fixed functions. These include 3D GPUs, MP3 audio decoding, digital video encode/decode, and Digital Signal Processing (DSP) functions such as Viterbi coding, DCT (Discrete Cosine Transform), and FFT (Fast Fourier Transform).
[ไม่มีภาพประกอบ]
The Silicon IP Business Model
The development of silicon intellectual property (SIP) has created a specialized ecosystem of vendors, ranging from individual developers to multi-billion-dollar corporations globally.
Companies utilizing this model are known as fabless semiconductor companies. They do not manufacture physical chips; instead, they facilitate the development process for customers—typically other semiconductor firms or module developers—by offering functional blocks. By licensing well-tested blocks, a company can fabricate a complex device while significantly reducing the time and cost associated with in-house design.
Industry Evolution and Market Value
The industry saw early growth in the 1990s and 2000s with companies like Virtual Chips, Sand Microelectronics, Integrated Intellectual Property (I2P), and Ingot Systems, focusing on standards like DDR3, USB, and PCI. Today, "star IP" companies such as ARM Holdings and Synopsys dominate the market. As early as 2005, the Gartner Group estimated the total value of silicon IP sales at US $1.5 billion, with an expected annual growth rate of approximately 30%.
| Feature | Soft IP Cores | Hard IP Cores |
|---|---|---|
| Format | RTL (Register Transfer Level) | GDSII (Layout) |
| Flexibility | High (Target multiple foundries) | Low (Specific to one technology) |
| Risk | Higher fabrication risk | Low (Pre-verified) |
| Performance | Variable | Predictable characteristics |
IP Hardening
IP hardening is the process of converting a proven soft core design into a hard (hardware) core. For instance, a DSP developed in RTL format can be targeted toward various foundries to create different physical implementations.
The primary advantage of hard IP is its predictability; because it is pre-implemented, it removes much of the guesswork from fabrication. Hardening involves evaluating design goals, target technology quality, and methodology. A hard core in GDSII format is considered "clean" if it passes DRC (Design Rule Checking) and LVS (Layout Versus Schematic), ensuring it meets all the foundry's manufacturing requirements.
Free and Open-Source IP
The landscape of chip design has been democratized by open-source initiatives. Since 2000, OpenCores.org has provided various soft cores, primarily written in Verilog and VHDL, under licenses such as the BSD-like or GNU General Public License.
Since 2010, the RISC-V initiative has led to a massive expansion in available IP cores, with nearly 50 available by 2019. This movement has fostered global collaboration in the creation of more secure and efficient hardware designs.
Frequently Asked Questions
What is the difference between a soft core and a hard core?
A soft core is a flexible, programmable design typically provided in RTL format that can be adapted to different manufacturing processes. A hard core is a pre-implemented, verified layout (GDSII) optimized for a specific technology, offering predictable performance but less flexibility.
Why are RISC architectures more common in IP cores than CISC?
RISC (Reduced Instruction Set Computer) architectures require less logic to implement than CISC (Complex Instruction Set Computer) architectures like x86. This makes RISC designs smaller and more efficient for embedded systems.
What does it mean for a hard core to be "clean"?
A hard core is considered clean when it passes Design Rule Checking (DRC) and Layout Versus Schematic (LVS) verification, meaning it adheres to all the physical manufacturing requirements set by the semiconductor foundry.
What is a fabless semiconductor company?
A fabless semiconductor company is a firm that designs and licenses silicon intellectual property (SIP) or develops chip designs but does not own the physical fabrication plant (fab) used to manufacture the chips.
Where can I find open-source IP cores?
Open-source soft cores can be found through platforms like OpenCores.org or through initiatives such as RISC-V, which provide designs under licenses like the GNU General Public License or BSD.