An in-depth analysis of the 80x86 processor families identi es architectural properties that may have unexpected, and undesirable, results in secure computer systems. In addition, reported implementation errors in some processor versions render them undesirable for secure systems because of potential security and reliability problems. In this paper, we discuss the imbalance in scrutiny for hardware protection mechanisms relative to software, and why this imbalance is increasingly di cult to justify as hardware complexity increases. We illustrate this di culty with examples of architectural subtleties and reported implementation errors.