Termos e Definições - M
The microcode is normally written by the CPU engineer during the design phase. It is generally not meant to be visible or changeable by a normal programmer, not even an assembly programmer, one of the reasons being that microcode (by design) can be dramatically changed with a new microarchitecture generation. Machine code often retains backwards compatibility. Microcode has often been used to let one microarchitecture emulate another, usually more powerful, architecture.
Some hardware vendors, especially IBM, also use the term microcode as a synonym for firmware, whether or not it actually implements the microprogramming of a processor. Even simple firmware, such as the one used in a hard drive, is sometimes described as microcode. Such use is not discussed here.
In computing, firmware is a computer program that is embedded in a hardware device, for example a microcontroller. It can also be provided on flash ROMs or as a binary image file that can be uploaded onto existing hardware by a user.
As its name suggests, firmware is somewhere between hardware and software. Like software, it is a computer program which is executed by a microprocessor or a microcontroller. But it is also tightly linked to a piece of hardware, and has little meaning outside of it.
MAPICS (Manufacturing Accounting and Production Information Control System)
A manufacturing enterprise resource planning (ERP) product, originally introduced by IBM as software for the AS/400 and earlier System/36 and System/38 systems. MAPICS was later taken over by Marcam, and separated into an independent company in 1997.
MSU (million service units)
Performance/capacity ratings assigned to IBM S/390 and zSeries systems, and compatible mainframes from Hitachi and Amdahl. MSUs are generally comparable to millions of instructions per second (MIPS), with one MSU equaling between 5.5 and 6.0 MIPS. Historically, all S/390-class software, both from the hardware vendors and independent software vendors, is priced based on server capacity, as determined by performance data. Pricing schemes such as Parallel Sysplex License Charge are based on MSUs.
MVS (Multiple Virtual Storage)
IBM's flagship mainframe operating system. Eventually superseded by OS/390 and, later, z/OS.
A version of MVS limited to 24-bit addressing and lacking the dynamic channel subsystem. It was dropped from support in the early 1990s.
MVS/ESA (Multiple Virtual Storage/Enterprise Systems Architecture)
A version of MVS introduced by IBM in 1988, capable of addressing up to 16 terabytes of data.