Adrian E. Seigler

Functional verification of the IBM system z10 processor chipset

This paper describes the comprehensive verification effort of the IBM System z10™ processor chipset, which consists of the z10™ quad-core central processor chip and the companion z10 symmetric multiprocessor (SMP) chip. The z10 processor chipset represented a significant redesign of its predecessor and thus presented a new challenge to ensure complete functional correctness of the product before the construction of actual system hardware. The z10 microprocessor pipeline was completely redesigned to support a doubling of the operating frequency. It also includes new hardware performance features, such as enhanced branch prediction, a reoptimized cache hierarchy, hardware-based prefetching, and a hardware implementation of decimal floating-point arithmetic in IEEE formats. In addition, there were significant hardware changes in the SMP storage hierarchy for optimized data latency performance. These changes include a new system topology, interprocessor book protocol, larger SMP size, and various aggressive cache ownership schemes. Key verification innovations are described, and a direct relationship to improved z10 system quality is provided for most cases.

Formal Verification of Partial Good Self-Test Fencing Structures

The concept of applying partial fencing to logic built-in self test (LBIST) hardware structures for the purpose of using partially good chips is well known in the chip design industry. Deceptively difficult though is the task of verifying that any particular implementation of partial fencing logic actually provides the desired behavior of blocking down-stream impact of all signals from fenced interfaces, and also ensuring that the partial fencing does not inadvertently preclude any common logic from being fully tested. In this paper we discuss a case study for a verification method which exploits the power of formal verification to prove that any given partial fencing design satisfies all behavioral expectations. We describe the details of the verification method and discuss the benefits of using this approach versus using traditional simulation methods. We also discuss the testbenches created as part of applying this new method. Furthermore, we discuss the formal verification algorithms that were employed during application of the method along with the tuning that was done to enable efficient completion of the verification tasks at hand.