nx_x86_modrm_gate.nx

nx_x86_modrm_gate.nx -- R1.0b: ModR/M + memory operands. Program round-trips a value through memory via [disp16] and [BX], does a memory-operand ADD, and a register-direct ModR/M MOV; checks both registers and the actual memory contents. Proves the 16-bit addressing core that real DOS programs depend on. B8 34 12 MOV AX,0x1234 89 06 00 02 MOV [0x200],AX (mod00 rm6 disp16 store) 8B 1E 00 02 MOV BX,[0x200] (mod00 rm6 disp16 load) -> BX=0x1234 03 1E 00 02 ADD BX,[0x200] (memory-operand add) -> BX=0x2468 89 1E 02 02 MOV [0x202],BX -> mem[0x202]=0x2468 89 D9 MOV CX,BX (mod11 register-direct) -> CX=0x2468 BB 00 03 MOV BX,0x300 89 07 MOV [BX],AX (mod00 rm7 [BX] store) -> mem[0x300]=0x1234 8B 17 MOV DX,[BX] (mod00 rm7 [BX] load) -> DX=0x1234 F4 HLT