A data path is the ALU, the set of registers, and the CPU's internal bus(es) that allow data to flow between them.[2]
The simplest design for a CPU uses one common internal bus.
Efficient addition requires a slightly more complicated three-internal-bus structure.[3]
Many relatively simple CPUs have a 2-read, 1-write register file
connected to the 2 inputs and 1 output of the ALU.
During the late 1990s, there was growing research in the area of reconfigurable data paths—data paths that may be re-purposed at run-time using programmable fabric—as such designs may allow for more efficient processing as well as substantial power savings.[4]
FSMDs are essentially sequential programs in which statements have been scheduled into states, thus resulting in more complex state diagrams. Here, a program is converted into a complex state diagram in which states and arcs may include arithmetic expressions, and those expressions may use external inputs and outputs as well as variables. The FSMD level of abstraction is often referred to as the register-transfer level.
FSMs do not use variables or arithmetic operations/conditions, thus FSMDs are more powerful than FSMs. An FSMD is equivalent to a Turing machine in expressiveness.
References
^ abNull, Linda; Lobur, Julia (2006). The Essentials of Computer Organization and Architecture. Jones & Bartlett Learning. p. 2016. ISBN978-0-7637-3769-6. All computers have a CPU that can be divided into two pieces. The first is the datapath, which is a network of storage units (registers) and arithmetic and logic units... connected by buses... where the timing is controlled by clocks.
^Zhu, Jianwen; Gajski, Daniel D. (1999-03-01). "A unified formal model of ISA and FSMD". Proceedings of the seventh international workshop on Hardware/Software codesign - CODES '99. New York, NY, USA: Association for Computing Machinery. pp. 121–125. doi:10.1145/301177.301504. ISBN978-1-58113-132-1. S2CID5426988.