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In May 2020, a script reading directly from the Control Register Bus (CRBUS) [34] (after exploiting "Red Unlock" in JTAG USB-A to USB-A 3.0 with Debugging Capabilities, without D+, D− and Vcc [35]) was used to read from the Local Direct Access Test (LDAT) port of the Intel Goldmont CPU and the loaded microcode and patch arrays were read. [36]
Machine code is generally different from bytecode (also known as p-code), which is either executed by an interpreter or itself compiled into machine code for faster (direct) execution. An exception is when a processor is designed to use a particular bytecode directly as its machine code, such as is the case with Java processors.
In practice, the processor implements an instruction set architecture named the Internal Microprogrammed Interface (IMPI) using a horizontal microcode format. The so-called vertical microcode layer implements the System/38's hardware-independent Machine Interface (MI) instruction set by translating MI code to IMPI code and executing it.
In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. [1] A device or program that executes instructions described by that ISA, such as a central processing unit (CPU), is called an implementation of that ISA.
Machine code is the form in which code that can be directly executed is stored on a computer. It consists of machine language instructions, stored in memory, that perform operations such as moving values in and out of memory locations, arithmetic and Boolean logic, and testing values and, based on the test, either executing the next instruction in memory or executing an instruction at another ...
The XSAVE instruction set extensions are designed to save/restore CPU extended state (typically for the purpose of context switching) in a manner that can be extended to cover new instruction set extensions without the OS context-switching code needing to understand the specifics of the new extensions.
Several computer systems introduced in the 1960s, such as the IBM System/360, DEC PDP-6/PDP-10, the GE-600/Honeywell 6000 series, and the Burroughs B5000 series and B6500 series, support two CPU modes; a mode that grants full privileges to code running in that mode, and a mode that prevents direct access to input/output devices and some other hardware facilities to code running in that mode.
In the x86 architecture, the CPUID instruction (identified by a CPUID opcode) is a processor supplementary instruction (its name derived from CPU Identification) allowing software to discover details of the processor.