X86 general purpose registers

How? I have heard that x86-64 processor has more general purposes registers but they are unnamed. 696k 109 748 1k. fyi/Arch1001. Special purposes register are, as the name implies, registers which are designed for just a task. Eight 32-bit general-purpose registers (e. In your generated code, it gets a snapshot of the stack pointer ( rsp) so that when adjustments are made to rsp (i. 128 general-purpose integer registers r0 through r127, each carrying 64 value bits and a trap bit. Contribute to 0pie/x86-Registers-cheat-sheet development by creating an account on GitHub. A few instructions use SI and DI as pointers to source and destination addresses when copying a block of data (e. On the other hand, 64-bit registers begin with r. Further, most compilers ignore the register keyword and optimize the register usage automatically. 2; SSE registers in 10. x86-64 “General Purpose” Registers Many “general purpose” registers have special purposes and conventions associated such as Return Value: %rax / %eax / %ax Function Args 1 to 6: %rdi, %rsi, %rdx, %rcx, %r8, %r9 Stack Pointer (top of stack): %rsp Old Code Base Pointer: %rbp, historically start of current stack frame but is The general-purpose registers are used to temporarily store data as it is processed on the processor. , What special purpose does the ECX register serve? and more. Registers esi and edi are source and destination index registers for array and string operations. Purpose. The register names for the first eight registers are mostly historical in nature; the last eight registers were give. Jun 10, 2014 · x86_64 has 16 general-purpose registers. Apr 19, 2013 at 20:21. These registers can be used for Mar 7, 2012 · Using Microsoft's 32 bit ABI ( cdecl or stdcall or other calling conventions), EAX, EDX and ECX are scratch registers (call clobbered). To store more than 8 bits, we have to use two registers in pairs. My approach is to allocate an array containing the values of the 16 registers and then read the array at index i. We usually use these names in our Registers can be used in your software directly with instructions such as mov, add or cmp. answered Mar 30, 2010 at 12:47. 64-bit 32-bit 16-bit 8 high bits 8 low bits Description Jun 24, 2022 · There are 8 general-purpose registers in the 8086 microprocessor. The basic architecture of the x86-64 is described in Volume 1 of the System Developer’s Manual. Jan 22, 2020 · First and foremost, you have to use registers that support the instructions you want to use. The least significant 8 bits of the first four of these registers are accessible via the AL, BL, CL, and DL in all execution modes Nov 30, 2015 · 2 General purpose registers. General Purpose Registers The eight 32-bit general-purpose registers are eax, ebx, ecx, edx, esi, edi, ebp, and esp. This graphic shows the register usage for Linux 64 Oct 24, 2016 · As others have indicated, they have special uses with the string instructions. Feb 26, 2011 · The canonical reference for all aspects of the x86 architecture can be found in the Intel Processor Manuals. x86 exposes the Debug Registers separately. 1 Extended Accumulator Register (EAX) 2. In the 64 bit x86 architecture there are 16 general purpose registers registers. 2; MMX registers in 9. W30). The lower 32/16/8 bits of these registers are referred to as rXd, rXw and rXb. It was added in 2003 during the transition to 64-bit processors. The 8080, 8085 and Z80 had 8-bit registers A, B, etc. Group of answer choicesTrueFalse Your solution’s ready to go! Enhanced with AI, our expert help has broken down your problem into an easy-to-learn solution you can count on. The first eight of these registers also have special names for historic reasons, they are, in order, rax, rbx, rcx, rdx, rsp, rbp, rsi, rdi. In fact eflags is as far away from a general purpose Study with Quizlet and memorize flashcards containing terms like The eight general purpose registers, Width of each register in a modern x86 processor, Breakdown of EAX and more. The x86-64 processors have 4 more general-purpose registers than the x86 processors. Feb 4, 2012 · I've been trying to learn 32-bit Intel x86 nasm syntax assembly on my Linux OS, and I've run into a question about the four general purpose 32-bit registers. Jul 20, 2018 · 11. ebp was the base pointer which pointed to the base of the current stack frame. The Nios II architecture provides thirty-two 32-bit general-purpose registers, r0 through r31. Fresh features from the #1 AI-enhanced learning platform. You can declare register variables in a function, but that does not specify which specific registers are used. , AX) Each 16-bit register can be addressed as two 8-bit registers (e. For the first part of the project, we shall use only five of the x86-64’s sixteen general-purpose registers. For example, the zero register ( r0) always returns the value zero, and writing to zero has no effect. My questions are: I need to use 32 registers as general purposes registers. ) The only one of the base 8 general-purpose registers that isn't "special" or used implicitly by any common instructions is EBX. I am writing a simple NASM assembly program which will get the value of one of 16 64-bit registers ( rax thru r15) when given a long number i ( 0 thru 15) corresponding to that register. X30), or as a 32-bit W register (W0. The Flags Register (RFLAGS) – Also called the status register or controls register. May 24, 2015 · 2. 1. pop ds. x86-64 processors offer us other kinds of registers. Lecture, Like C++ variables, registers are actually available in several sizes: rax is the 64-bit, "long" size register. x86-64 also expands general-purpose registers to 64-bit, and expands the number of them from 8 (some of which had limited or x86 architecture general purpose registers traditional general purpose registers : 6 3 : 3 2: 3 1 : 1 6: 1 5 : 8: 7 : 0: RAX or R0: zero-extended: EAX or R0D Nov 26, 2021 · Get certified by completing the course. It can The architecture provides 31 general purpose registers. Nov 12, 2023 · 1. They also can be employed as pointers to reference data items in memory. Some CPU architectures include additional sets of registers, e. The EFLAGS register is a 32 bit register. You can watch this class without ads and with extra learning games, quizzes, and lab setup instructions by going to https://ost2. srcp [srcidx++] = argv [j]; compiles into Eight general purpose registers on x86. 8 7AH BH CHAL BLmemory mode: all the segment registers are loaded with the same segment selector so that all memory Modern (i. The x86 processor traces its heritage at least as far back as the Created by. 4; FPU registers in 8. 3. CPU Registers x86. It is of 16 bits and is divided into two 8-bit registers AH and AL to also perform 8-bit instructions. These registers are mainly used to perform address calculations, arithmetic and logical calculations. 7 Extended Source Index (ESI) 2. In AMD64/x86_64. It is technically a volatile register, since the value isn't preserved. Using registers instead of memory to store values makes the process faster and cleaner. By default, SI is offset from the DS data segment, DI is offset from the ES extra segment, but either or both of these can be overridden. The registers are like variables built in the processor. And Registers In the assembly syntax accepted by gcc, register names are always prefixed with %. All of these registers are 64 bits wide. Nov 30, 2022 · Learn about the types and functions of general purpose registers in x86 architecture. MSRs. eax is a 32-bit general-purpose register with two common uses: to store the return value of a function and as a special register for certain calculations. It will be faster to do the xor with vpxor, however, mulx does not have an AVX2 equivalent. The registers are stored on the stack in the following order: EAX, ECX, EDX, EBX, ESP (original value), EBP, ESI, and EDI (if the current operand-size attribute is 32) and AX, CX, DX, BX, SP (original value), BP, SI, and DI (if the operand-size attribute is 16). There is an additional user-visible program counter pc register which holds the address of the current instruction. Take certain double register multiply and divide instructions, for example, which specifically involve eax and edx in particular Code Obfuscation. The x86-64 execution unit contains 16 64-bit general-purpose registers, which are used to perform arithmetic, logical, compare, data transfer, and address calculation operations. The AX, DX, CX, BX, BP, DI, and SI registers are 16-bit equivalents of the above, they represent the low-order 16 bits of 32-bit registers. icted in Figure 1. Chapter 19 discusses the x86-64 SIMD execution units. That's how memory protection was implemented. , AH and AL) 31. The leading e stands for e xtended and means that your register is 32 bits wide. Oct 22, 2020 · The traditional separation between General Purpose Registers and Floating-Point Registers is reflected in the ptrace(2) CPU-specific calls that allow setting or getting either the GPR or FPU registers in a single operation. General Purpose Registers 64-bit Register 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. (These instructions reverse the operation of the PUSHA Meaning. I did say [i]eight [/i] general purpose registers. One way they cut down was by giving registers dedicated functions. The term "x64" includes both AMD 64 and Intel64. Other general purpose registers cannot form an effective address. – user180742. We'll learn more about the trap bit later. The E stands for extended. Four of the GPRs can be treated as a 32-bit quantity, a 16-bit quantity or as two 8-bit quantities. We can just take advantage of the fact that SSE instructions are generally less known. The registers have evolved dramatically over time and continue to do so. From what I've been thinking, eax was a 32-bit register that was supposed to be used with the 16-bit register ax, which was subdivided into ah (upper 8 bits), and al (lower 8 bits). igknighton. 4. My code is as follows: SECTION . Each register is 64 bits wide; the lower 32-, 16- and 8-bit portions are selectable by a pseudo-register name. 8 Extended Destination Index (EDI) 3 Extended Instruction Pointer (EIP) 4 Aug 7, 2017 · general purpose in general means you can use it in general for instructions. x86 / 32 bit mode In 32 bit mode i. on Linux and x86): Is it true that without calling syscall, a regular C program will not (implicitly) use any of general-purpose registers? linux By default BX, SI and DI registers work with DS segment register; BP and SP work with SS segment register. General-Purpose Registers. For example, RAX used to be EAX (in the 32-bit machine), which used to be called the Dec 7, 2023 · These general purpose registers can also be addressed as 8-bit registers. x86 the notion of general purpose is a bit odd as the instruction set didnt start that way and was sort of mangled into it later, but if you can encode a register into the various instructions like add, sub, xor, mul, as well as loads and stores and other such things, then it can be used generally across the The x86_64 instruction set architechture includes 16 general purpose regisers, each of which can be addressed in full, or by the lower 32, 16 and 8 bits. 3 Applicator Program, OS, BIOS, Hardware. Find out how they store data, instructions, and pointers for CPU operations. General-Purpose Registers The x86-64 core execution unit contains 16 64-bit general-purpose registers, which are used to perform arithmetic, logical, and address calculations. Jump to navigation Jump to search. g. Dec 1, 2016 · 16 registers per core? – mdpc. This is because, in x86-64, the GPRs have had their width (used to refer to storage capacity, in this case) extended from 32 bits to 64 bits, but the legacy 32 bit, 16 bit and 8 bit registers are Jun 22, 2020 · General Purpose Register (GPR) plays a key role in any computer architecture. The Intel x86 processor uses complex instruction set computer (CISC) architecture, which means there is a modest number of special-purpose registers instead of large quantities of general-purpose registers. Some registers are designated for a certain purpose, such as %rsp being used as the stack pointer or %rax for Sep 29, 2022 · Hey there, is it possible to have x86 general purpose registers while debugging with codelldb extension? Also i've noticed that LLDB itself is using x64 asm registers, can this be caused by it? Also tried to tweak things in LLDB like "target. Additionally, scalar operation can be extended to vector operation to confuse a third-side reverser. Media Registers; Segment Registers; We will cover each of these categories below. These can hold operands for arithmetic as well as logical operations. Functions use these registers to perform integer arithmetic, bitwise logical operations, comparisons, address calculations, and data transfers. For calculations, we will use eax, ebx, ecx, and edx. For example, cs, ds, gs and the other segment registers fall into the special purpose registers, because they exist to hold segments' number. May 27, 2020 at 17:18. . For example these are both valid. For example, storing current register content when there is an interruption. The core eight 16-bit registers are AX, BX, CX, DX, SI, DI, BP, and SP. strings). 2. Furthermore IA-32 general had 32bit internal registers as well, so it couldn't page. General Purpose Registers. The registers were extended to 64 bits: rax … rdx, rsp etc. It provides a new 64-bit mode and a legacy 32-bit mode, which is identical to x86. In fact, there are only 4 instructions that allow you to address the eflags register as a whole: PUSHF, POPF, SAHF, and LAHF And even these instructions only act upon a limited set of bits within the register. Application Programmers generally use only the general purpose registers, floating point registers, XMM, and YMM registers. You can assume that the C compiler will generate code that will be preserving rbx, rbp, rsi, rdi, and r12 thru r15. They can be accessed by all 16-bit Thumb instructions and all 32-bit Thumb-2 instructions. For real mode programming, the ES segment register must be used with DI and DS with SI as in. The EAX, EDX, ECX, EBX, EBP, EDI, and ESI registers are 32-bit general-purpose registers, used for temporary data storage and memory access. Using a data size of 16 bits will cause only the bottom 16 bits of the 32-bit general-purpose registers to be modified – the top 16 bits are left unchanged. This register becomes architectural in AMD64 and has been adopted by Intel. The AH, DH, CH, and BH registers The 64-bit x86 register set consists of 16 general purpose registers, only 8 of which are available in 16-bit and 32-bit mode. movsb es:di, ds:si SI and DI can also be used as general purpose index registers. Pops doublewords (POPAD) or words (POPA) from the stack into the general-purpose registers. As you can see, it isn't talking about all registers here, it's only talking about general-purpose registers (The list after this excerpt which I think you are talking about is also only showing general-purpose registers). The lower 32 bits, 16 bits, and 8 bits of each register are directly addressable in operands. Dec 21, 2023 · The x64 architecture is a backwards-compatible extension of x86. ) The default OperandSize and AddressSize to use for each instruction is given by the D bit of the segment descriptor of the current code segment - D=0 makes both 16-bit, D=1 makes both 32 If the interrupt handler code is simply a stub that forwards to C code, you don't need to save all of the registers. 2 RegistersModern 64-bit x86 processors have sixteen 64-bit general purpose registers, as de. Sep 19, 2019 · The x86 architecture contains eight 32-bit General Purpose Registers (GPRs). mov ax, 5000h. However, the word “address registers” is not commonly used to describe anything on x86. When running in 64bit mode, the number of general purpose registers is doubled (in addition to their size being doubled). 6 Extended Base Pointer (EBP) 2. Dec 7, 2018 · General-Purpose Registers. This is real mode (no address translation). 2 Extended Base Register (EBX) 2. These registers are not always used for the purposes illustrated below. 1 General Purpose Registers R0 through R7. But mov ds, 5000h is not a valid x86 instruction. 8086 processorLet us consider an 8086 processor. 3 Extended Counter Register (ECX) 2. The number of physical registers is also different as there are rename registers to support out-of-order execution. Mar 30, 2010 · It stands for a general purpose register. Sep 8, 2023 · All x86-64 processors contain 16 64-bit wide general-purpose registers. An x86 CPU has eight main registers in its scalar register file in 32-bit mode: EAX, EBX, ECX, EDX, ESI, EDI, EBP, and ESP. What are the CPU general purpose registers - General purpose registers are additional registers that are present in CPU which is used for either memory address or data whenever needed. It's an x86 hardware limitation, not a Windows limitation. Some registers have names recognized by the assembler. The register names are mostly historical. Each register can store 8 bits. General-purpose registers are used for holding x86_64. Register Purpose Saved across calls %rax return value No %rsp stack pointer Yes %rbp base pointer Yes x86 Real Mode General Purpose Registers SI and DI are general purpose registers. rbp is the frame pointer on x86_64. 5 Extended Stack Pointer (ESP) 2. x64 extends x86's 8 general-purpose registers to be 64-bit, and adds 8 new 64-bit registers. FS and GS are commonly used by OS kernels to access thread-specific memory. , EAX) Each lower-half can be addressed as a 16-bit register (e. Model-Specific Registers. All registers are prefixed with "E" to denote that they are 32-bit registers, rather General-Purpose Registers. Jan 16, 2012 · General Purpose Registers. x64 General-Purpose Registers (GPRs) In the x64 architecture, there are 16 general-purpose registers, each capable of holding 64 bits of data. The condition codes in EFLAGS are call-clobbered. Initially, when the instruction set May 8, 2015 · This is a general question (e. It is generally used for arithmetical and logical instructions but in 8086 microprocessor it is not mandatory to have an accumulator as the General-Purpose Registers. mov ds, ax. For example, the C source code. AX: This is the accumulator. All of these have various special uses, but of them, the eighth, ESP, has the most special status as the stack pointer. Implementing a 16-bit processor with only 20,000 active transistors was quite a tour-de-force. e 386 and beyond) x86 processors have eight 32-bit general purpose registers, as depicted in Figure 1. The set of general-purpose registers is expanded from 8 to 16. Register ebp is the base pointer. As such, x86-32 (and x86-16 before it) really couldn't use the same registers for both, and x86-64 was intentionally designed to resemble x86-32, hence kept the register architecture roughly similar. eax. SI, DI These registers are usually used as offsets into data space. They also can be used as temporary storage locations for constant values, intermediate results, and pointers to data values stored in memory. Each register can be used as a 64-bit X register (X0. IP - the instruction pointer: May 27, 2020 · It only really makes sense to do this if your general-purpose registers are at least 64 bits. e. In x86-32 and x86-64 assembly, 16 bit instructions such as. 8 are carried over from x86 (eax, ebx, ecx, edx, esi, edi, ebp, esp), and 8 are brand new (r8 through r15). 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. Numbering CPU registers is the norm, almost any processor does that. Description ¶ . push 5000h. This section will look at the 8 general purpose registers on the x86 architecture. The instruction sets are almost identical. SP mentioned later in this chapter. In windows, the GS register is used to manage thread-specific memory. The other general-purpose integer registers are call-preserved. From OSDev Wiki. Sep 29, 2013 · In 8086 assembly programming, we can only load a data into a segment register by, first loading it into a general purpose register (or memory) and then we have to move it from there to the segment register. Each register pair can store a maximum of 16-bit data. Registers are the fastest kind of memory available in the machine. Registers. The EAX register is the 32 bit version of the AX register. 2, 10. The table below lists the commonly used registers (sixteen general-purpose plus two special). Dec 5, 2022 · General purpose registers. In Windows 64-bit the GS register is used to point to operating system defined structures. Bit (s) Label. The 8086 processor however is ancient, they had an extremely limited transistor budget back in 1976. e x86 architecture there are 8 general purpose registers. Feb 27, 2016 · We have 16 general purpose registers in x86-64 processors: RAX, RCX, RDX, RBX, RSP, RBP, RSI, RDI, R9-15. With 64-bit mode and the new paging mode, it supports vastly larger amounts of virtual memory and physical memory than was possible on its 32-bit predecessors, allowing programs to store larger amounts of data in memory. You should only need to save and restore rax, rcx, rdx, and r8 thru r11. The 64-bit registers have names beginning with "r", so for example the 64-bit extension of eax is called rax. © 2024 Google LLC. The main features include: Pointers and long integers are 64 bits long. Many instructions on x86 (and other architectures, though less so) have some restrictions on how registers are supported. For example, this register diagram shows that W0 is the bottom 32 bits of X0, and W1 is the bottom 32 bits of X1: 4. There are 4 register pairs AX, BX, CX, DX. eax is the 32-bit, "int" size register. The main tools to write programs in x86 assembly are the processor registers. sequential numbers. The registers are loaded in the following order: EDI, ESI, EBP, EBX, EDX, ECX, and EAX (if the operand-size attribute is 32) and DI, SI, BP, BX, DX, CX, and AX (if the operand-size attribute is 16). Integer arithmetic operations support 8, 16, 32, and 64-bit data types. For example, RAX used to be EAX (in the 32-bit machine), which used to be called the Sep 6, 2016 · (Look up these ALU instructions online or the original PDF of Intel's instruction reference manual—see the x86 tag wiki for links. They are all 32 bits; the reset value is unpredictable. General-purpose registers (64-bit naming conventions) [+/-] 틀:Main 64-bit x86 adds 8 more general-purpose registers, named R8, R9, R10 and so on up to R15. – Nate Eldredge. A function can also store an intermediate or temporary result in a general-purpose register instead of saving it to memory. Apr 4, 2021 · From the link you provided, there is an excerpt: x64 extends x86's 8 general-purpose registers to be 64-bit, and adds 8 new 64-bit registers. Register growth in the x86 CPU family has come about by extending registers existing in older CPUs. x86-32 general-purpose registers 8, 32-bit registers for integers or pointers In encoding order: eax ,ecx ,edx ,ebx ,esp ,ebp , esi ,edi Without the e , refers to the low 16-bits of the 32-bit register Every register is special esp : used as stack pointer by stack accesses ebp : used as frame pointer by enter /leave Mar 1, 2022 · RISC-V base ISA consists of 31 general-purpose registers x1-x31 which hold integer values. 2. For example, say within a small piece of code, there are four 64-bit unsigned integers, I will need four xor, two mulx from BMI2. Dec 27, 2021 · The 8086 microprocessor has 8 registers each of 8 bits, AH, AL, BH, BL, CH, CL, DH, DL as shown below. Modern (i. When Intel expanded the x86 architecture to 32 bits in 1986, it doubled the size Sep 15, 2019 · The registers on a 64 bit CPU are 64 bits wide. 1. Guffa. 4 Extended Data Register (EDX) 2. 18. All registers are prefixed with "E" to denote that they are 32-bit registers, rather than their 16-bit counterparts. esp was the stack pointer. There are also 16 SIMD registers and 8 x87 registers. Contents. The segment registers separated kernel space and userspace addresses. They are named r0, r1, r2, r3 … r15. The number of registers on a modern x86 CPU is well beyond what the CPU reveals - the CPU maintains shadow registers which are renamed as needed based upon the instruction flow. The 16 bit AX register can be addressed as AH (high byte) and AL (low byte). The changeover from general-purpose registers to SSE registers can be used for simple code obfuscation as well. There are eight 16-bit general-purpose registers: AX, BX, CX, DX, BP, SI, DI, and SP; and you can place any value in them that may be expressed in 16 bits or fewer. Clayton: SIMD registers are probably only usable for SIMD instructions. In the 32-bit world, however, any register may serve as a memory offset Figure 1: Sizes of standard data types with x86-64 Both long integers and pointers require 8 bytes, as compared to 4 for IA32. reserving space for local variables or push ing values on to the stack), local variables and function parameters are still accessible from a constant offset from rbp. 128 floating point registers f0 through f127. Is it possible. Several Nov 17, 2016 · The motivation is that, sometime it is faster to do some things in AVX2 while others with general purpose register. The register x0 is hardwired to the constant 0. The following diagram is taken directly from Chapter 3 in this volume: Registers. DF=0 is required on call/return so you can use rep movsb without a cld first. EBX: The Base Register. It was added in 1985 during the transition to 32-bit processors with the 80386 CPU. General purpose registers were added: r8 … r15. Register esp is the stack pointer. The new registers are named r8 through r15. It also means that complex special-purpose instructions will predominate. Jun 24, 2012 · The upper 56 bits or 48 bits (respectively) of the destination general-purpose register are not be modified by the operation. On x64, an operation that writes to a 32-bit register zero-extends the result. The SP register is the stack pointer. Some registers are designated for a certain purpose, such as %rsp being used as the stack pointer or %rax for x86 Registers. . It is a pointer to the “top" of the stack. In 16-bit mode, the base register, EBX, acts as a general-purpose pointer. data Registers in x86 Assembly. mov ax, bx Nov 18, 2009 · x64 extends x64's 8 general-purpose registers to be 64-bit, and adds 8 new 64-bit registers. level. default-arch" neither of this helped at all. This video talks about the structure of General Purpose Registers (GPR) of the Jan 29, 2017 · 159. Pushes the contents of the general-purpose registers onto the stack. The problem with the x86 serie of processors is that there are few registers to use. For example, EAX used to be called the accumulator since it was used by a number of arithmetic operations, and ECX was known as the counter since it was used to hold a loop index. In past days, registers had very specific functions. We will focus on 32-bit x86 architecture for our purposes. This table gives all the basic registers, with special-purpose registers highlighted in yellow. x86_64. May 30, 2012 · They have no processor-defined purpose, but instead are given purpose by the OS's running them. 5. Besides the specialized ESI, EDI, and EBP registers, it is the only general-purpose register that can appear in a square-bracket memory access (For example, MOV [BX], AX). Each new version of general-purpose registers is created to be backward compatible with previous processors. May 20, 2010 · Not necessarily. The register documentation is a bit spread out, but you can find them in: Volume 1 - General purpose registers in section 3. RISC-V does not define a specific subroutine return address link register, but it does Jun 11, 2010 · Which registers do you want to access? General purpose registers normally can not be accessed from C. Its MSR number is 0xC0000080. May 8, 2017 · You cannot specify EFLAGS as an explicit source or destination in any instruction. Also, although BX can form an effective address, BH and BL cannot. SPECIAL PURPOSE REGISTERS. @PaulA. Dec 10, 2020 · X86 just has general purpose registers, though in 16 bit mode, only bx, si, di, and bp could be used for explicit memory operands (sp is used for a bunch of implicit memory operands). Apr 19, 2013 at 21:31. Study with Quizlet and memorize flashcards containing terms like What are the x86 processor's three basic modes of operation?, Name all eight 32-bit general purpose registers. Control processor-specific features. It also introduces a new naming convention that must be used for these new registers and can also be used for the old ones (except that AH, CH, DH and BH have no equivalents). The order in which they are listed here is for a reason: it is the same order that is used in a push-to-stack operation. x86-64 has 14 general-purpose registers and several special-purpose registers. These are two separate ways of looking at the same register. eax, ecx etc are sgeneral purpose register because you can use them for everything without (almost) no The table below lists the commonly used registers (sixteen general-purpose plus two special). The R0 through R7 general purpose registers are also called low registers. So AX = AH (high 8-bit) and AL (low 8-bit). wj nt kb dg nn ui bx eu ww lv