What is the difference between a processor, a chip, a socket, and a core?
Following are brief definitions for common terms related to supercomputers:
- Recent developments in computational architecture can lead to
confusion concerning what a microprocessor is. Since the advent of
multi-core technology, such as dual-cores and quad-cores, the term
"processor" has been used to describe a logical execution unit or a
physical chip. A multi-core chip may have several cores. With the
advent of multi-core technology, the term "processor" has become
context-sensitive, and is largely ambiguous when describing large
multi-core systems. Essentially a core comprises a logical execution
unit containing an L1 cache and functional units. Cores are able to
independently execute programs or threads. Supercomputers are listed as having
thousands of cores.
- A chip refers to a physical integrated circuit (IC) on a computer.
A chip in the context of this document refers to an execution unit
that can be single- or multi-core technology.
The socket refers to a physical connector on a computer motherboard
that accepts a single physical chip. Many motherboards can have
multiple sockets that can in turn accept multi-core chips.
- A process is an independent program running on a computer. A
process has a full stack of memory associated for its own use, and
does not depend on another process for execution. MPI
(Message Passing Interface) processes are true processes because they
can run on independent machines or the same machine.
A thread is essentially a process that does not have a full stack of
memory associated for it. The thread is tied to a parent process, and is
merely an offshoot of execution. Typically thread processes must run on
the same computer, but can execute simultaneously on separate cores of
the same node. OpenMP parallelism uses threads for child processes.
Hyper-threading is an Intel technology that originally preceded
multi-core systems, and was used to make a single core appear
logically as multiple cores on the same chip. Intel abandoned
hyper-threading briefly during the advent of multi-core processors but
reintroduced the technology in 2008. Since then, Intel has used it
extensively to improve the performance of parallel computations in its
multi-core processors. Hyper-threading improves performance by sharing
the computational workload between multiple cores whenever possible,
allowing the operating system to schedule more than one process at a
time. For more, see Intel
Multi-core compute nodes can be described by the number of execution
units, or cores. A computer with 8 cores would be described as an 8-way
node. This machine can have 8 independent processes running
simultaneously. A 32-core system would be called a 32-way node.
- As explained above, a processor could describe either a single execution core or a single physical multi-core chip. The context of use will define the meaning of the term.
This document was developed with support from National Science Foundation (NSF) grant OCI-1053575. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.
Last modified on April 22, 2013.