Explore the Power of CXL Memory Subsystem - A Demo of Type 3 Memory Device

Table of Contents

1. Introduction
2. Motherboard Design
3. CPU and DDR5 DIMMs
4. CXL Component and PCIe Chem Slot
5. Intel FPGA and DDR4 Memory Controllers
6. CXL 2.0 Device Interface
7. System Boot Process
8. System Recognition and Link Training
9. CXL Device Enumeration and Mapping
10. Memory Mapping into System Memory
11. Memory testing
12. Conclusion

Introduction

Today, I'm going to walk you through our proof of concept for our CXL memory subsystem. This article will provide an in-depth overview of the different components involved and how they work together to create a high-performance memory solution. We'll start by discussing the motherboard design and then move on to the specific components, such as the CPU, DDR5 DIMMs, CXL component, and Intel FPGA. We'll also explore the system boot process, device recognition, memory mapping, and testing. So, let's dive in and explore the world of CXL memory!

Motherboard Design

The foundation of the CXL memory subsystem is the motherboard. Our next-generation motherboard is specifically designed to accommodate the various components required for seamless integration. It provides the necessary connections and slots for the CPU, memory controllers, CXL component, and other crucial elements. The motherboard acts as the central hub, allowing efficient communication and data transfer between the different components.

CPU and DDR5 DIMMs

At the heart of our CXL memory subsystem lies the CPU and DDR5 DIMMs. We utilize an Intel pre-production Sapphire Rapid CPU, renowned for its high performance and reliability. Alongside the CPU, we have the DDR5 DIMMs, which play a crucial role in storing and retrieving data efficiently. The combination of a powerful CPU and high-speed DDR5 memory ensures optimal system performance and responsiveness.

CXL Component and PCIe Chem Slot

For the CXL component, we have designed it to fit seamlessly into a standard PCIe chem slot. This allows for easy installation and compatibility with existing systems. On the CXL card, we have implemented an Intel pre-production FPGA (Field-Programmable Gate Array), which enhances the capabilities of the memory subsystem. The FPGA acts as a bridge between the CPU, memory controllers, and other components, enabling efficient data transfer and management.

Intel FPGA and DDR4 Memory Controllers

On one side of the CXL card, we have the Intel FPGA, which serves as a management interface for the memory subsystem. It allows us to monitor the system, perform firmware updates, and Collect valuable information such as errors and performance metrics. On the other side of the card, we have two DDR4 memory controllers. Each memory controller is connected to a standard DDR4 register DIMM, providing a total capacity of 64 gigabytes (two DIMMs, each 32 gigabytes).

CXL 2.0 Device Interface

One of the key features of our CXL memory subsystem is the integration of a CXL 2.0 device interface on the FPGA. This interface enables us to interact with the memory subsystem at a higher level, providing advanced management capabilities. With the device interface, we can easily monitor errors, collect diagnostic information, and update the firmware as needed. It ensures the efficient operation and long-term reliability of the CXL memory subsystem.

System Boot Process

Now, let's explore how the system boots up and recognizes the CXL memory subsystem. As the system powers on, it goes through a series of steps to detect and initialize the installed devices. The system firmware first recognizes the presence of the CXL device and proceeds to train the link between the CPU and the CXL component. This link training ensures a stable and high-speed connection, with a transfer rate of 32 giga transfers per Second (Gen 5).

System Recognition and Link Training

Once the link between the CPU and CXL component has been successfully trained, the system firmware identifies the device as a CXL device instead of a PCIe device. This recognition is based on the specific hardware configuration and allows the firmware to properly enumerate and map the CXL memory device into the system memory. This seamless integration ensures efficient utilization of the memory resources and optimized system performance.

CXL Device Enumeration and Mapping

After the system has recognized the CXL device, it proceeds to enumerate and map it into the system memory. This involves associating the device with the appropriate resources and allocating memory space accordingly. In the case of our CXL memory subsystem, the device is mapped as a separate NUMA (Non-Uniform Memory Access) node, labeled as NUMA Node 2. The system firmware takes care of this mapping process, ensuring that the memory subsystem is seamlessly integrated into the overall system architecture.

Memory Mapping into System Memory

Now that the CXL memory device has been correctly enumerated and mapped, let's take a closer look at how it is integrated into the system memory. By examining the PNEUMA CTL output, we can see a total of three NUMA nodes. Two of these nodes correspond to the CPUs with their associated CPU cores and local DDR5 memory. The third node, NUMA Node 2, represents the CXL device, which does not have any CPUs associated with it but boasts a total of 64 gigabytes of memory. This memory capacity aligns with what we have installed on the CXL card, ensuring accurate mapping and seamless integration.

Memory Testing

With the system up and running and the CXL memory subsystem properly mapped, it's time to test the memory itself. We conduct a series of comprehensive tests to ensure that the memory is functioning as expected and delivering the desired performance levels. These tests cover various aspects of memory functionality and stress-test the system under different scenarios. By assessing the test results and verifying that they pass successfully, we can confirm that the memory is working optimally and is ready for extensive usage.

Conclusion

In conclusion, our proof of concept for the CXL memory subsystem showcases the power and versatility of this innovative technology. Through meticulous design and integration, we have created a high-performance memory solution that leverages the power of the CPU, DDR5 DIMMs, CXL component, and Intel FPGA. With seamless system recognition, efficient memory mapping, and comprehensive testing, we have achieved optimal performance and reliability. The CXL memory subsystem is set to revolutionize the way we utilize memory in modern computing systems, opening up new possibilities for improved performance and scalability.

Highlights

• Our proof of concept for the CXL memory subsystem demonstrates the power and versatility of this innovative technology.
• The motherboard design serves as the foundation for seamless integration of the various components.
• The Intel pre-production Sapphire Rapid CPU and DDR5 DIMMs ensure high performance and responsiveness.
• The CXL component fits into a standard PCIe chem slot, enhancing compatibility and ease of installation.
• The Intel FPGA serves as a management interface, facilitating system monitoring and firmware updates.
• The CXL 2.0 device interface provides advanced management capabilities and seamless integration.
• The system boot process involves device recognition, link training, and proper enumeration of the CXL memory device.
• Memory mapping ensures the efficient utilization of resources and optimized system performance.
• Comprehensive memory testing guarantees the functionality and performance of the CXL memory subsystem.
• The CXL memory subsystem opens up new possibilities for improved performance and scalability in modern computing systems.

FAQ

Q: What is the CXL memory subsystem? A: The CXL memory subsystem is an innovative technology that integrates high-performance memory into the overall system architecture, leveraging the power of the CPU, DDR5 DIMMs, and specialized components.

Q: How does the CXL memory subsystem improve system performance? A: The CXL memory subsystem enhances system performance by providing faster data transfer rates, optimized memory utilization, and seamless integration into the system architecture.

Q: Can the CXL memory subsystem be used in existing systems? A: Yes, the CXL memory subsystem is designed to be compatible with standard PCIe chem slots, allowing for easy integration into existing systems.

Q: What advantages does the CXL 2.0 device interface offer? A: The CXL 2.0 device interface provides advanced management capabilities, allowing for efficient system monitoring, firmware updates, and error collection.

Q: How is the CXL memory subsystem tested? A: The CXL memory subsystem undergoes comprehensive testing to ensure its functionality and performance, covering various memory functionalities and stress-testing the system under different scenarios.

Q: What are the benefits of NUMA mapping in the CXL memory subsystem? A: NUMA mapping allows for efficient utilization of memory resources, ensuring optimal performance and scalability in multi-core systems.

Q: Can the CXL memory subsystem be scaled for higher capacities? A: Yes, the CXL memory subsystem can be scaled by increasing the number of CXL cards and memory modules, enabling higher memory capacities for demanding applications.

Q: Is the CXL memory subsystem compatible with different operating systems? A: Yes, the CXL memory subsystem is designed to be compatible with various operating systems, ensuring seamless integration and optimal performance.

Q: How does the CXL memory subsystem contribute to overall system reliability? A: The CXL memory subsystem, with its advanced management capabilities and comprehensive testing, ensures long-term reliability and stable operation in demanding computing environments.

Q: What future developments can we expect for the CXL memory subsystem? A: The CXL memory subsystem holds immense potential for future developments, including higher memory capacities, improved performance, and enhanced compatibility with emerging technologies.

Resources

PCI-SIG - The Consortium behind CXL