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Nemesis (computing)
Encyclopedia
Nemesis is an operating system
designed by the University of Cambridge
, the University of Glasgow
, the Swedish Institute of Computer Science
and Citrix Systems
.
Nemesis was conceived with multimedia
uses in mind. In a microkernel
environment, an application
is typically implemented by a number of processes, most of which are servers performing work on behalf of more than one client. This leads to enormous difficulty in accounting for resource usage. In a kernel
-based system, multimedia applications spend most of their time in the kernel, leading to similar problems.
The guiding principle in the design of Nemesis was to structure the operating system in such a way that the majority of code could execute in the application process itself. Nemesis therefore had an extremely small lightweight kernel and performed most operating system functions in shared libraries, which executed in the user's process.
The ISA
s that Nemesis supports include x86 (Intel i486, Pentium
, Pentium Pro
, and Pentium II
), Alpha
and ARM
(StrongARM
SA-110). Nemesis also runs on evaluation boards (21064 and 21164).
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
designed by the University of Cambridge
University of Cambridge
The University of Cambridge is a public research university located in Cambridge, United Kingdom. It is the second-oldest university in both the United Kingdom and the English-speaking world , and the seventh-oldest globally...
, the University of Glasgow
University of Glasgow
The University of Glasgow is the fourth-oldest university in the English-speaking world and one of Scotland's four ancient universities. Located in Glasgow, the university was founded in 1451 and is presently one of seventeen British higher education institutions ranked amongst the top 100 of the...
, the Swedish Institute of Computer Science
Swedish Institute of Computer Science
The Swedish Institute of Computer Science, SICS, is an independent non-profit research organization with a research focus on applied computer science. The institute carries out research in a number of areas, including networked embedded systems, future Internet technologies, large scale...
and Citrix Systems
Citrix Systems
Citrix Systems, Inc. is a multinational corporation founded in 1989, that provides server and desktop virtualization, networking, software-as-a-service , and cloud computing technologies, including Xen open source products....
.
Nemesis was conceived with multimedia
Multimedia
Multimedia is media and content that uses a combination of different content forms. The term can be used as a noun or as an adjective describing a medium as having multiple content forms. The term is used in contrast to media which use only rudimentary computer display such as text-only, or...
uses in mind. In a microkernel
Microkernel
In computer science, a microkernel is the near-minimum amount of software that can provide the mechanisms needed to implement an operating system . These mechanisms include low-level address space management, thread management, and inter-process communication...
environment, an application
Application software
Application software, also known as an application or an "app", is computer software designed to help the user to perform specific tasks. Examples include enterprise software, accounting software, office suites, graphics software and media players. Many application programs deal principally with...
is typically implemented by a number of processes, most of which are servers performing work on behalf of more than one client. This leads to enormous difficulty in accounting for resource usage. In a kernel
Monolithic kernel
A monolithic kernel is an operating system architecture where the entire operating system is working in the kernel space and alone as supervisor mode...
-based system, multimedia applications spend most of their time in the kernel, leading to similar problems.
The guiding principle in the design of Nemesis was to structure the operating system in such a way that the majority of code could execute in the application process itself. Nemesis therefore had an extremely small lightweight kernel and performed most operating system functions in shared libraries, which executed in the user's process.
The ISA
Instruction set
An instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...
s that Nemesis supports include x86 (Intel i486, Pentium
Pentium
The original Pentium microprocessor was introduced on March 22, 1993. Its microarchitecture, deemed P5, was Intel's fifth-generation and first superscalar x86 microarchitecture. As a direct extension of the 80486 architecture, it included dual integer pipelines, a faster FPU, wider data bus,...
, Pentium Pro
Pentium Pro
The Pentium Pro is a sixth-generation x86 microprocessor developed and manufactured by Intel introduced in November 1, 1995 . It introduced the P6 microarchitecture and was originally intended to replace the original Pentium in a full range of applications...
, and Pentium II
Pentium II
The Pentium II brand refers to Intel's sixth-generation microarchitecture and x86-compatible microprocessors introduced on May 7, 1997. Containing 7.5 million transistors, the Pentium II featured an improved version of the first P6-generation core of the Pentium Pro, which contained 5.5 million...
), Alpha
DEC Alpha
Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computer instruction set architecture developed by Digital Equipment Corporation , designed to replace the 32-bit VAX complex instruction set computer ISA and its implementations. Alpha was implemented in microprocessors...
and ARM
ARM architecture
ARM is a 32-bit reduced instruction set computer instruction set architecture developed by ARM Holdings. It was named the Advanced RISC Machine, and before that, the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in numbers produced...
(StrongARM
StrongARM
The StrongARM is a family of microprocessors that implemented the ARM V4 instruction set architecture . It was developed by Digital Equipment Corporation and later sold to Intel, who continued to manufacture it before replacing it with the XScale....
SA-110). Nemesis also runs on evaluation boards (21064 and 21164).
See also
- ExokernelExokernelExokernel is an operating system kernel developed by the MIT Parallel and Distributed Operating Systems group, and also a class of similar operating systems....
- XenXenXen is a virtual-machine monitor providing services that allow multiple computer operating systems to execute on the same computer hardware concurrently....
- Kernel-wide design approaches