What is LAHF and Sahf?

LAHF stands for Load AH from Flags and SAHF stands for Store AH into Flags. LAHF & SAHF are used to load and store instructions for certain status flags. Instructions are basic commands composed of one or more symbols that that are passed to a CPU as input.

What is the purpose of LAHF instruction?

LAHF and SAHF are load and store instructions, respectively, for certain status flags. These instructions are used for virtualization and floating-point condition handling. The flag control instructions provide a method for directly changing the state of bits in the flag register.

How many registers does x86-64 have?

8 registers
As well, 64-bit x86 includes SSE2, so each 64-bit x86 CPU has at least 8 registers (named XMM0–XMM7) that are 128 bits wide, but only accessible through SSE instructions.

What is Sahf Assembly?

Store AH into Flags (sahf)

What is LAHF in assembly language?

Load Flags into AH Register (lahf)

Do I need x86 or AMD64?

PC (Intel x86) For almost all PCs. 64-bit PC (AMD64) Choose this to take full advantage of computers based on the AMD64 or EM64T architecture (e.g., Athlon64, Opteron, EM64T Xeon, Core 2). If you have a non-64-bit processor made by AMD, or if you need full support for 32-bit code, use the Intel x86 images instead.

What is CLD in assembly language?

CLD: clear direction flag so that string pointers auto increment after each string operation. STD: std is used to set the direction flag to a 1 so that SI and/or DI will automatically be decremented to point to the next string element when one of the string instruction executes.

What is Pushf instruction?

PUSHF simply pushes the current contents of the Flags register onto the top of the stack. The Flags register is not affected when you push the flags, but only when you pop them back with POPF.

Who invented x86?

Intel
x86 is a family of instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant.

What are LAHF & SAHF CPU instructions?

Many virtualization admins know what NX/XD is but LAHF & SAHF CPU instructions are a processor function that you have probably never heard of. LAHF stands for Load AH from Flags and SAHF stands for Store AH into Flags. LAHF & SAHF are used to load and store instructions for certain status flags.

When did Intel start supporting LAHF instructions?

Support for LAHF and SAHF instructions appeared shortly after NX/XD was introduced. AMD introduced support for the instructions with their Athlon 64, Opteron and Turion 64 revision D processors in March 2005 and Intel introduced support for the instructions with the Pentium 4 G1 stepping in December 2005.

Do you know what NX/XD & lahF/SAHF are?

Most of the requirements are fairly straightforward, the 64-bit CPU requirement has been there since vSphere 4 was introduced, but many people probably don’t know what NX/XD & LAHF/SAHF are. The NX/XD bit is a CPU feature called N ever e X ecute, hence the NX name.