Changes

*[https://userpages.umbc.edu/~squire/intel_book.pdf Intel Microprocessors Practical Reference] *[https://bitsavers.org/pdf/ibm/pc/GG24-3057-00_IBM_PC_Internals_Fundamentals_Course_Notes_198603.pdf IBM PC Internals Fundamentals Course] *[https://bitsavers.org/pdf/ibm/pc/pc/6025008_PC_Technical_Reference_Aug81.pdf IBM PC Hardware Technical Reference] *[http://bitsavers.org/pdf/ibm/pc/pc_jr/PCjr_Technical_Reference_Nov83.pdf IBM PCjr Hardware Technical Reference] *[http://www.retroarchive.org/dos/docs/ibm5160techref.pdf IBM PC XT Hardware Technical Reference] *[https://bitsavers.org/pdf/ibm/pc/at/1502494_PC_AT_Technical_Reference_Mar84.pdf IBM PC AT Hardware Technical Reference] *[https://bitsavers.org/pdf/ibm/pc/dos/6172220_DOS_1.0_Jan82.pdf IBM Disk Operating System 1.0 Reference]