“The EU-funded research project is now over, so the project is not active anymore. Nemesis currently runs on a large number of platforms including x86 based PCs, DEC Alpha workstations and evaluation boards (2104) and StrongARM SA-110 based network computers.Īustin Donnelly, previously member of the Nemesis project team (which was mostly consisted by universities and research labs), told OSNews about the project: Despite the fact that there is a single system-wide page table mapping virtual addresses to physical addresses, memory protection is still performed on a per-process basis. The single address space also removes the need to copy high-bandwidth multimedia data. By use of a single address space, Nemesis greatly reduces memory-system related context-switch penalties.
Providing QoS to time-sensitive applications necessarily requires more frequent context-switches. This leads to a vertically-structured operating system. Nemesis therefore has an extremely small lightweight kernel, and performs most operating system functions in shared libraries which execute in the user’s process. 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. In a kernel-based system, multimedia applications spend most of their time in the kernel, leading to similar problems. This leads to enormous difficulty in accounting for resource usage. In a microkernel environment like Nemesis’, an application is typically implemented by a number of processes, most of which are servers performing work on behalf of more than one client.
Screenshots are available but read more for information and status of this interesting operating system. The OS has been built with the Multimedia in mind, its sole purpose of existance was the delivery and performance of multimedia content in the best way possible. Nemesis provides fine-grained guaranteed levels of all system resources including CPU, memory, network bandwidth and disk bandwidth. Nemesis is an operating system written from scratch (but it does retain some Posix compatibility layer for easy application porting), whose design is geared to the support of time-sensitive applications requiring a consistent ‘Quality of Service’ (QoS), such as those which use multimedia.
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