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How many instructions are in x86-64?
al. states that the current x86-64 design “contains 981 unique mnemonics and a total of 3,684 instruction variants” [2]. However they do not specify which features are included in their count.
How many general-purpose registers are there in x86-64?
8 General-Purpose Registers
The x86 architecture has 8 General-Purpose Registers (GPR), 6 Segment Registers, 1 Flags Register and an Instruction Pointer. 64-bit x86 has additional registers.
What is x86-64 assembly?
For years, PC programmers used x86 assembly to write performance-critical code. x64 is a generic name for the 64-bit extensions to Intel’s and AMD’s 32-bit x86 instruction set architecture (ISA). AMD introduced the first version of x64, initially called x86-64 and later renamed AMD64.
How many registers are there in x64?
8
Registers. x64 extends x86’s 8 general-purpose registers to be 64-bit, and adds 8 new 64-bit registers. The 64-bit registers have names beginning with “r”, so for example the 64-bit extension of eax is called rax. The new registers are named r8 through r15.
Is AMD a x64?
AMD64 is a 64-bit processor architecture that was developed by Advanced Micro Devices (AMD) to add 64-bit computing capabilities to the x86 architecture.
Do you sign-extend the register to 64 bits?
If the result of an 8-bit or 16-bit operation is intended for 64-bit address calculation, explicitly sign-extend the register to the full 64-bits. don’t show this kind of “strange” behaviour that the upper word of eax is zeroed.
Why did the 80386 add 32-bit registers?
When the 80386 added 32-bit registers, no facilities were provided to access just the top half of a register, but an instruction like ROR ESI,16 would be fast enough that there could still be value in being able to hold two 16-bit values in ESI and switch between them.
When do you add a prefix to a 64 bit register?
This prefix is added (automatically by assemblers) when an operand contains a 64-bit register. Note: The instruction pointer can only be used in RIP-relative addressing, which was introduced with long mode. All these are 16 bits long.
What is the extended feature enable register in AMD K6?
Extended Feature Enable Register (EFER) is a model-specific register added in the AMD K6 processor, to allow enabling the SYSCALL/SYSRET instruction, and later for entering and exiting long mode. This register becomes architectural in AMD64 and has been adopted by Intel.