Memory + Interfaces

PCIe 4.0 SerDes PHY

The Rambus PCI Express (PCIe) 4.0 SerDes PHY is designed to maximize interface speed in the difficult system environments found in high-performance computing. It is a low-power, area-optimized, silicon-proven IP designed with a system-oriented approach to maximize flexibility and ease integration for our customers. The PCIe 4 SerDes PHY supports PCIe 4.0, 3.0, and 2.0 and has full support for manufacturability.


Product Brief

How Rambus PCIe 4.0 Works

The Rambus PCIe 4.0 SerDes PHY is a high-performance serial link subsystem. Optimized for power in challenging, high-loss channels, our PCIe 4.0 PHYs are ideal for networking, storage and data center systems.

PCIe 4.0 SerDes PHY Subsystem Example

The PHYs come complete with a PMA hard macro that supports PCIe 4.0, 3.0, and 2.0 protocols and a physical coding sublayer (PCS) soft macro for PCIe that is PIPE4.2 compliant. They have a minimal set of broadside control and are configurable in x2, x4 and x8 lane configurations. This gives the PHYs improved flexibility and support for a wide range of applications. The PCIe 4.0 PHYs are rigorously tested through third party compliance testing and internal interoperability system testing.

In order to improve system margin and performance, our solution features transmit and receive equalization and full equalization adaptation. This ensures that data is recovered even in the presence of channel and system interference.

Our PCIe 4 SerDes PHYs are available on TSMC, Global Foundry and Samsung process nodes.

Solution Offerings

Protocol Compatibility

ProtocolData Rate (Gbps)Application
PCIe 2.04High bandwidth peripherals and graphics cards
PCIe 3.08Enterprise solutions and chip to chip connectivity
PCIe 4.016Hyperscale data center and big data applications

SerDes Signal Integrity Challenges at 28Gbps and Beyond

Maintaining signal integrity has become increasingly difficult as data rates moves past 28Gbps to 56Gbps and beyond. Up to 28Gbps rates, NRZ is the preferred and standardized encoding scheme which consists of 1’s and 0’s. NRZ is also referred to as PAM2 (pulse amplitude modulation, 2-level), due to its two amplitude levels which contain 1 bit of information in every symbol. With serial data rates hitting 56 Gb/s per channel, signal impairments caused by increased bandwidth has prompted the high-speed serial data industry to adopt PAM4, or 4-level pulse amplitude modulation. For PAM4 signals, the baud rate equals one-half the bit rate and the Nyquist frequency equals one-fourth the bit rate. Compared to PAM2/NRZ, PAM4 cuts the bandwidth for a given data rate in half by transmitting two bits in each symbol. This allows engineers to double the bit rate in the channel without doubling the required bandwidth.

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Phase Interpolator-based CDR


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