NASM 2.05 based x86 Instruction Reference[ch102]
A.5.82 FIDIV, FIDIVR: Floating-Point/Integer Division FIDIV mem16 ; DE /6 [8086,FPU] FIDIV mem32 ; DA /6 [8086,FPU] FIDIVR mem16 ; DE /7 [8086,FPU] FIDIVR mem32 ; DA /7 [8086,FPU] FIDIV divides ST0 by the 16-bit or 32-bit integer stored in the given memory location, and stores the result in ST0. FIDIVR does the division the other way up: it divides the integer by ST0, but still stores the result in ST0.