Instruction Set Architecture (ISA)

void add(){
  int a, b, c;
  a = 2;
  b = 2;
  c = a * b;
}

ARM Family

• 64-bit version: aarch64

• 32-bit version: aarch32

• In the ARM world, a bunch of hardware reference designs are available. Therefore ARM hardware/cpus are more standardized than x86 counterparts

• The decoding of instructions on ARM is quite simple and straightforward compared to x86
• ARM is open license. Therefore anyone can created chips on top of it.

add:
    sub   sp, sp, #16
    mov   w8, #2
    str   w8, [sp, #12]
    str   w8, [sp, #8]
    ldr   w8, [sp, #12]
    ldr   w9, [sp, #8]
    mul   w8, w8, w9
    str   w8, [sp, #4]
    add   sp, sp, #16
    ret

• RISC Architecture (Reduced Instruction Set Computing)
• Offers few instructions, but faster execution

Intel x86 Family

• 64-bit version: x86-64, x64, x86_64, AMD64, Intel 64
• 32-bit version: A-32 (Intel Architecture, 32-bit), i386

add:
    push  rbp
    mov   rbp, rsp
    mov   dword ptr [rbp - 4], 2
    mov   dword ptr [rbp - 8], 2
    mov   eax, dword ptr [rbp - 4]
    imul  eax, dword ptr [rbp - 8]
    mov   dword ptr [rbp - 12], eax
    pop   rbp
    ret

• CISC Architecture (Complex Instruction Set Computing)
• Has more assembly instructions than RISC processors
• Good for when developers had to write assembly code directly