NASM 2.05 based x86 Instruction Reference[ch089]
A.5.69 FBLD, FBSTP: BCD Floating-Point Load and Store FBLD mem80 ; DF /4 [8086,FPU] FBSTP mem80 ; DF /6 [8086,FPU] FBLD loads an 80-bit (ten-byte) packed binary-coded decimal number from the given memory address, converts it to a real, and pushes it on the register stack. FBSTP stores the value of ST0, in packed BCD, at the given address and then pops the register stack.