Collaborate Disseminate
Video gamers know about cheat codes, but assembly language programmers are often in search of undocumented instructions. One way to find them is to map out all of a CPU’s …read more Continue reading Finding Undocumented 8086 Instructions Via Microcode
Though it is largely forgotten today, the Intel 80286 was for a while in the 1980s the processor of choice and designated successor to the 8086 in the world of …read more Continue reading The 286 Gives Up One Of Its Final Secrets
For an old CPU, finding all the valid instructions wasn’t very hard. You simply tried them all. Sure, really old CPUs might make it hard to tell what the instruction …read more Continue reading Undocumented x86 Instructions Allow Microcode Access
There was a time when owning computer meant you probably knew most or all of the instructions it could execute. Your modern PC, though, has a lot of instructions, many of them meant for specialized operating system, encryption, or digital signal processing features.
There are known undocumented instructions in a lot of x86-class CPUs, too. What’s more, these days your x86 CPU might really be a virtual machine running on a different processor, or your CPU could have a defect or a bug. Maybe you want to run sandsifter–a program that searches for erroneous or undocumented instructions. Who knows what …read more
