Category Archives: 8086/8088

The IBM PC, 41 Years Ago

No, the OS/2 Museum does not have either a time machine or difficulty doing basic math. As of this writing, it is August 2021 and the IBM PC was announced in August 1981, 40 years ago. But in August 1980, … Continue reading

Posted in 8086/8088, BIOS, DOS, IBM, Intel, PC hardware, PC history | 60 Comments

Undocumented 8086 Opcodes, Part I

This is a guest post by Raúl Gutiérrez Sanz This multi-part document is about undocumented 8086 processor opcodes and their behavior. Most of the document will likely apply to the 8088 processor as well, but this has not been verified. … Continue reading

Posted in 8086/8088, Intel, Undocumented | 12 Comments

Undocumented 8086 Opcodes

A minor mystery recently surfaced while analyzing DOS boot sectors. DOS uses several criteria when deciding whether a boot sector contains a valid BPB, and one of the criteria is (oddly enough) checking whether the first two bytes of the … Continue reading

Posted in 8086/8088, Documentation, Intel, x86 | 62 Comments