Eye Diagram Optimization based on Design of Experiments (DoE) to Accelerate Industrial Testing of High Speed Links

Higher data rates in high speed input/output (HSIO) links demand more equalization (EQ) complexity, leading to an ever larger number of possible combinations of EQ settings. Finding the optimal set of EQ parameters through exhaustive methods is prohibitive given the time-to-market requirements. This paper presents a methodology to design a statistically sufficient set of experiments for optimizing the receiver eye diagram of a HSIO link while greatly reducing the overall testing time. Our methodology is illustrated by a 5-Gbps HSIO link comprised of a Tx, a channel (including packages, vias, PCB traces, connectors and a crosstalk aggressor) and an Rx

Jitter Tolerance Acceleration Using the Golden Section Optimization Technique

Post-silicon validation of high-speed input/output (HSIO) links is a critical process for product qualification schedules of computer platforms under the current time-to-market (TTM) commitments. The goal of post-silicon validation for HSIO links is to confirm design robustness of both receiver (Rx) and transmitter (Tx) circuitry in a real application environment. One of the most common ways to evaluate the performance of a HSIO link is to characterize the Rx jitter tolerance (JTOL) performance by measuring the bit error rate (BER) through the link under worst stressing conditions. However, JTOL testing is very time-consuming when executing at specification BER, and the testing time is extremely increased when considering manufacturing process, voltage, and temperature (PVT) test coverage for a qualification decision. In order to speed up this process, we propose a new approach for JTOL testing based on the golden section algorithm. The proposed method takes advantage of the fast execution of the golden section search with a high BER, while overcoming the lack of correlation between different BERs by performing a downward linear search at the actual target BER until no errors are seen. Our proposed methodology is validated by implementing it in a server HSIO link

High-Speed Links Receiver Optimization in Post-Silicon Validation Exploiting Broyden-based Input Space Mapping

One of the major challenges in high-speed input/output (HSIO) links electrical validation is the physical layer (PHY) tuning process. Equalization techniques are employed to cancel any undesired effect. Typical industrial practices require massive lab measurements, making the equalization process very time consuming. In this paper, we exploit the Broyden-based input space mapping (SM) algorithm to efficiently optimize the PHY tuning receiver (Rx) equalizer settings for a SATA Gen 3 channel topology. We use a good-enough surrogate model as the coarse model, and an industrial post-silicon validation physical platform as the fine model. A map between the coarse and the fine model Rx equalizer settings is implicitly built, yielding an accelerated SM-based optimization of the PHY tuning process

Fast jitter tolerance testing for high-speed serial links in post-silicon validation

Post-silicon electrical validation of high-speed input/output (HSIO) links is a critical process for product qualification schedules of high-performance computer platforms under current aggressive time-to-market (TTM) commitments. Improvements in signaling methods, circuits, and process technologies have allowed HSIO data rates to scale well beyond 10 Gb/s. Noise and EM effects can create multiple signal integrity problems, which are aggravated by continuously faster bus technologies. The goal of post-silicon validation for HSIO links is to ensure design robustness of both receiver (Rx) and transmitter (Tx) circuitry in real system environments. One of the most common ways to evaluate the performance of a HSIO link is to characterize the Rx jitter tolerance (JTOL) performance by measuring the bit error rate (BER) of the link under worst stressing conditions. However, JTOL testing is extremely time-consuming when executed at specification BER considering manufacturing process, voltage, and temperature (PVT) test coverage. In order to significantly accelerate this process, we propose a novel approach for JTOL testing based on an efficient direct search optimization methodology. Our approach exploits the fast execution of a modified golden section search with a high BER, while overcoming the lack of correlation between different BERs by performing a downward linear search at the actual target BER until no errors are found. Our proposed methodology is validated in a realistic industrial server post-silicon validation platform for three different computer HSIO links: SATA, USB3, and PCIe3.ITESO, A.C

A Holistic Methodology for System Margining and Jitter Tolerance Optimization in Post-Silicon Validation

The optimization of receiver analog circuitry in modern high-speed input/output (HSIO) links is a very time consuming post-silicon validation process. Current industrial practices are based on exhaustive enumeration methods to improve either the system margins or the jitter tolerance compliance test. In this paper, these two requirements are addressed in a holistic optimization-based approach. We propose an innovative objective function based on these two metrics. Our method employs Kriging to build a surrogate model based on system margining and jitter tolerance measurements. The proposed method is able to deliver optimal system margins and guarantee jitter tolerance compliance while substantially decreasing the typical post-Si validation time

Machine learning techniques and space mapping approaches to enhance signal and power integrity in high-speed links and power delivery networks

Enhancing signal integrity (SI) and reliability in modern computer platforms heavily depends on the post-silicon validation of high-speed input/output (HSIO) links, which implies a physical layer (PHY) tuning process where equalization techniques are employed. On the other hand, the interaction between SI and power delivery networks (PDN) is becoming crucial in the computer industry, imposing the need of computationally expensive models to also ensure power integrity (PI). In this paper, surrogate-based optimization (SBO) methods, including space mapping (SM), are applied to efficiently tune equalizers in HSIO links using lab measurements on industrial post-silicon validation platforms, speeding up the PHY tuning process while enhancing eye diagram margins. Two HSIO interfaces illustrate the proposed SBO/SM techniques: USB3 Gen 1 and SATA Gen 3. Additionally, a methodology based on parameter extraction is described to develop fast PDN lumped models for low-cost SI-PI co-simulation; a dual data rate (DDR) memory sub-system illustrates this methodology. Finally, we describe a surrogate modeling methodology for efficient PDN optimization, comparing several machine learning techniques; a PDN voltage regulator with dual power rail remote sensing illustrates this last methodology.ITESO, A.C

System Margining Surrogate-Based Optimization in Post-Silicon Validation

There is an increasingly higher number of mixed-signal circuits within microprocessors. A significant portion of them corresponds to high-speed input/output (HSIO) links. Post-silicon validation of HSIO links is critical to provide a release qualification decision. One of the major challenges in HSIO electrical validation is the physical layer (PHY) tuning process, where equalization techniques are typically used to cancel any undesired effect. Current industrial practices for PHY tuning in HSIO links are very time consuming since they require massive lab measurements. On the other hand, surrogate modeling techniques allow to develop an approximation of a system response within a design space of interest. In this paper, we analyze several surrogate modeling methods and design of experiments techniques to identify the best approach to efficiently optimize a receiver equalizer. We evaluate the models performance by comparing with actual measured responses on a real server HSIO link. We then perform a surrogate-based optimization on the best model to obtain the optimal PHY tuning settings of a HSIO link. Our methodology is validated by measuring the real functional eye diagram of the physical system using the optimal surrogate model solution

A Holistic Formulation for System Margining and Jitter Tolerance Optimization in Industrial Post-Silicon Validation

There is an increasingly higher number of mixed-signal circuits within microprocessors and systems on chip (SoC). A significant portion of them corresponds to high-speed input/output (HSIO) links. Post-silicon validation of HSIO links can be critical for making a product release qualification decision under aggressive launch schedules. The optimization of receiver analog circuitry in modern HSIO links is a very time consuming post-silicon validation process. Current industrial practices are based on exhaustive enumeration methods to improve either the system margins or the jitter tolerance compliance test. In this paper, these two requirements are addressed in a holistic optimization-based approach. We propose a novel objective function based on these two metrics. Our method employs Kriging to build a surrogate model based on system margining and jitter tolerance measurements. The proposed method, tested with three different realistic server HSIO links, is able to deliver optimal system margins and guarantee jitter tolerance compliance while substantially decreasing the typical post-silicon validation time.ITESO, A.C

Transmitter and Receiver Equalizers Optimization Methodologies for High-Speed Links in Industrial Computer Platforms Post-Silicon Validation

As microprocessor design scales to nanometric technology, traditional post-silicon validation techniques are inappropriate to get a full system functional coverage. Physical complexity and extreme technology process variations introduce design challenges to guarantee performance over process, voltage, and temperature conditions. In addition, there is an increasingly higher number of mixed-signal circuits within microprocessors. Many of them correspond to high-speed input/output (HSIO) links. Improvements in signaling methods, circuits, and process technology have allowed HSIO data rates to scale beyond 10 Gb/s, where undesired effects can create multiple signal integrity problems. With all of these elements, post-silicon validation of HSIO links is tough and time-consuming. One of the major challenges in electrical validation of HSIO links lies in the physical layer (PHY) tuning process, where equalization techniques are used to cancel these undesired effects. Typical current industrial practices for PHY tuning require massive lab measurements, since they are based on exhaustive enumeration methods. In this work, direct and surrogate-based optimization methods, including space mapping, are proposed based on suitable objective functions to efficiently tune the transmitter and receiver equalizers. The proposed methodologies are evaluated by lab measurements on realistic industrial post-silicon validation platforms, confirming dramatic speed up in PHY tuning and substantial performance improvement