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The processor boots up using a set of microcode held inside the processor and stored in an internal ROM. [1] A microcode update populates a separate SRAM and set of "match registers" that act as breakpoints within the microcode ROM, to allow jumping to the updated list of micro-operations in the SRAM. [1]
The act of writing microcode is often referred to as microprogramming, and the microcode in a specific processor implementation is sometimes termed a microprogram. Through extensive microprogramming, microarchitectures of smaller scale and simplicity can emulate more robust architectures with wider word lengths, additional execution units , and ...
The XSAVE instruction set extensions are designed to save/restore CPU extended state (typically for the purpose of context switching) in a manner that can be extended to cover new instruction set extensions without the OS context-switching code needing to understand the specifics of the new extensions.
Transactional Synchronization Extensions (TSX), also called Transactional Synchronization Extensions New Instructions (TSX-NI), is an extension to the x86 instruction set architecture (ISA) that adds hardware transactional memory support, speeding up execution of multi-threaded software through lock elision.
If a CPU has an NX bit, it is more likely to be viewed as being a complex instruction set computer (CISC) or reduced instruction set computer (RISC). MISC chips typically lack hardware memory protection of any kind, unless there is an application specific reason to have the feature. If a CPU has a microcode subsystem, that excludes it from ...
AMD has not used K-nomenclature codenames in official AMD documents and press releases since the beginning of 2005, when K8 described the Athlon 64 processor family. AMD now refers to the codename K8 processors as the Family 0Fh processors. 10h and 0Fh refer to the main result of the CPUID x86 processor instruction.
Because a program normally relies on such factors, different systems will typically not run the same machine code, even when the same type of processor is used. A processor's instruction set may have fixed-length or variable-length instructions. How the patterns are organized varies with the particular architecture and type of instruction.
The processor might not perform well doing so. For example, Excavator through Zen 2 processors implement PEXT and PDEP instructions using microcode resulting in the instructions executing significantly slower than the same behaviour recreated using other instructions. [20]