Thomas Edison Yu

Thermal-Safe Test Access Mechanism and Wrapper Co-optimization for System-on-Chip

Smaller manufacturing processes have resulted in higher power densities which put greater emphasis on packaging and temperature control during test. For system-on-chips, peak power-based scheduling algorithms are used to optimize tests while satisfying power budgets. However, imposing power constraints does not necessarily mean that overheating is avoided due to the non-uniform power distribution across the chip. This paper presents a TAM/Wrapper co-design methodology for system-on-chips that ensures thermal safety while still optimizing the test schedule. The method combines a simplified thermal-cost model with a traditional bin-packing algorithm to minimize test time while satisfying temperature constraints. Experiments show that even minimal increases in test time can yield considerable decrease in test temperature as well as the possibility of further lowering temperatures beyond those achieved using traditional power-based test scheduling.

Using Domain Partitioning in Wrapper Design for IP Cores Under Power Constraints

This paper presents a novel design method for power-aware test wrappers targeting embedded cores with multiple clock domains. We show that effective partitioning of clock domains combined with bandwidth conversion and gated-clocks would yield shorter test times due to greater flexibility when determining optimal test schedules especially under tight power constraints

RedSOCs-3D: Thermal-safe test scheduling for 3D-stacked SOC

This paper investigates the challenges of a 3D-stacked system-on-chip testing, especially in terms of thermal problem. It is known that test power can be more than twice the intended power dissipation of the chip in the functional mode, for a single die. This problem is exacerbated when more than one dies are stacked on top of each other in a single package. Without proper test strategies, the thermal limit could be exceeded during test and this could permanently damage the possibly good chips. Using a heuristic approach, we proposed a set of rules that need to be followed when scheduling the core tests of each chip layer. These rules are based on the initial findings of 3D-chip test simulation using a commercial thermal simulation tool. Using these simple rules, it was found that up to 40% reduction in the peak temperature can be achieved when the thermal-aware test scheduling technique is employed.

Identifying Non-Robust Untestable RTL Paths in Circuits with Multi-cycle Paths

As LSI manufacturing technology improves and the time-to-market for products becomes stricter, more and more circuit designs have multiple clock domains due to concerns such as design re-use, power reduction and temperature control. It is not uncommon for these designs to have multi-cycle paths which are untestable. The rapid identification of these untestable paths reduces test generation time as well as over-testing due to design for testability (DFT). For current and future designs, this has already become impractical at the gate-level. This paper presents a method to identify nonrobust untestable multi-cycle paths at the register transfer level (RTL) and the details in a case study of a benchmark circuit.

Effective Domain Partitioning for Multi-Clock Domain IP Core Wrapper Design under Power Constraints

The rapid advancement of VLSI technology has made it possible for chip designers and manufacturers to embed the components of a whole system onto a single chip, called System-on-Chip or SoC. SoCs make use of pre-designed modules, called IP-cores, which provide faster design time and quicker time-to-market. Furthermore, SoCs that operate at multiple clock domains and very low power requirements are being utilized in the latest communications, networking and signal processing devices. As a result, the testing of SoCs and multi-clock domain embedded cores under power constraints has been rapidly gaining importance. In this research, a novel method for designing power-aware test wrappers for embedded cores with multiple clock domains is presented. By effectively partitioning the various clock domains, we are able to increase the solution space of possible test schedules for the core. Since previous methods were limited to concurrently testing all the clock domains, we effectively remove this limitation by making use of bandwidth conversion, multiple shift frequencies and properly gating the clock signals to control the shift activity of various core logic elements. The combination of the above techniques gains us greater flexibility when determining an optimal test schedule under very tight power constraints. Furthermore, since it is computationally intensive to search the entire expanded solution space for the possible test schedules, we propose a heuristic 3-D bin packing algorithm to determine the optimal wrapper architecture and test schedule while minimizing the test time under power and bandwidth constraints.

Thermal-Aware Test Access Mechanism and Wrapper Design Optimization for System-on-Chips

Rapid advances in semiconductor manufacturing technology have led to higher chip power densities, which places greater emphasis on packaging and temperature control during testing. For system-on-chips, peak power-based scheduling algorithms have been used to optimize tests under specified power constraints. However, imposing power constraints does not always solve the problem of overheating due to the non-uniform distribution of power across the chip. This paper presents a TAM/Wrapper co-design methodology for system-on-chips that ensures thermal safety while still optimizing the test schedule. The method combines a simplified thermal-cost model with a traditional bin-packing algorithm to minimize test time while satisfying temperature constraints. Furthermore, for temperature checking, thermal simulation is done using cycle-accurate power profiles for more realistic results. Experiments show that even a minimal sacrifice in test time can yield a considerable decrease in test temperature as well as the possibility of further lowering temperatures beyond those achieved using traditional power-based test scheduling.