Monthly Archives: December 2013

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

Installing Oct ’91 NT from CD

With VirtualBox 4.3, it is possible to install the oldest known pre-release of Windows NT directly from CD, the way Microsoft intended. This is the Fall ’91 Comdex preview which only supported the x86 architecture and a very short list … Continue reading

Posted in Microsoft, NT, SCSI | 35 Comments


I recently tried to revive an old ThinkPad 600 (with a 300 MHz mobile Pentium II processor). The system wouldn’t boot up and reported errors (173, 163) which are usually a good indication of a dead CMOS battery. In a … Continue reading

Posted in PC hardware, ThinkPad | 2 Comments