Intel Corporation publishes a number of books on the x86 family of processors:
Intel Corporation, 80386 Programmer's Reference Manual, 1986. ISBN 1-55512-022-9.
Intel Corporation, i486 Microprocessor Hardware Reference Manual, 1990. ISBN 1-55512-112-8.
Intel Corporation, Pentium Processor User's Manual - Volume 3: Architecture and Programming Manual, 1993. ISBN 1-55512-195-0.