Documentation Error on the LGDT Instruction

ID Number: Q34375

5.10 | 5.10

MS-DOS | OS/2

docerr

Summary:

The "Microsoft Macro Assembler 5.10 Reference Guide" states that

the LGDT instruction only takes a memory 64 operand while the Intel

manual states the LGDT instruction takes a memory 48 operand.

The MASM Reference is incorrect. The correct operand size is memory

48. These instructions load essentially a 2-field structure whose

total size is 48 bits. The first two bytes are the limit field and the

last four bytes are the base field. This can be defined using the DF

directive, or by defining a structure as described.