In November 2007 AMD stopped delivery of Barcelona processors after a bug in the translation lookaside buffer (TLB) of stepping B2 was discovered that could rarely lead to a race condition and thus a system lockup.
AMD K6 | AMD Accelerated Processing Unit | AMD K5 | List of AMD Phenom microprocessors#"Thuban" (E0, 45 nm, Hexa-core) | AMD's Athlon 64 | Advanced Micro Devices (AMD) |