Phenom/fɨˈnɒm/ is the 64-bitAMD desktop processor line based on the K10 microarchitecture, in what AMD calls family 10h (10 hex, i.e. 16 in normal decimal numbers) processors, sometimes incorrectly called "K10h". Triple-core versions (codenamed Toliman) belong to the Phenom 8000 series and quad cores (codenamed Agena) to the AMD Phenom X4 9000 series. The first processor in the family was released in 2007.
AMD considers the quad core Phenoms to be the first "true" quad core design, as these processors are a monolithic multi-core design (all cores on the same silicon die), unlike Intel's Core 2 Quad series which are a multi-chip module (MCM) design. The processors are on the Socket AM2+ platform.
Before Phenom's original release a flaw was discovered in the translation lookaside buffer (TLB) that could cause a system lock-up in rare circumstances; Phenom processors up to and including stepping "B2" and "BA" are affected by this bug. BIOS and software workarounds disable the TLB, and typically incur a performance penalty of at least 10%. This penalty was not accounted for in pre-release previews of Phenom, hence the performance of early Phenoms delivered to customers is expected to be less than the preview benchmarks. "B3" stepping Phenom processors were released March 27, 2008 without the TLB bug and with "xx50" model numbers.
An AMD subsidiary has released a patch for the Linux kernel, to overcome this bug by software emulation of accessed- and dirty-bits. This method causes less performance loss than previous workarounds. The program was said in December 2007 to have received "minimal functional testing."
AMD launched several models of the Phenom processor in 2007 and 2008 and an upgraded Phenom II in late 2008.
The model numbers of the Phenom line of processors were changed from the PR system used in its predecessors, the AMD Athlon 64 processor family. The Phenom model numbering scheme, for-later released Athlon X2 processors, is a four-digit model number whose first digit is a family indicator. Energy Efficient products end with an “e” suffix (for example, "Phenom 9350e"). Some Sempron processors use the prefix LE (for example, "Sempron LE-1200")