HP Vectra XU 6/XXX Optimization Manual page 8

Multithreaded Operating Systems
Any operating system consists of a number of functions, each of which controls some small
part of the PC's operation. Application software uses these functions as building blocks to
create specific, more powerful tools for the user.
Under a single threaded operating system no individual function is independent. All operating
system work (including any work performed by an application) consists of a single, inseparable
thread of functions and so must be performed by the same processor.
A multithreaded operating system uses functions that are effectively independent. This allows
the operating system to break its work into separate threads of functions. Since the threads are
effectively independent, they can be followed by different processors.
MPS-Ready Operating Systems
An MPS-ready operating system is multithreaded and also guarantees the integrity of any data
shared between the different processors. Data integrity is essential in any environment where
multiple copies of the same data can exist — failure to guarantee this can lead to logical
conflicts and operational failure. MPS-ready operating systems protect against these risks by
ensuring that valid copies of the same data are identical.
Multiprocessor- Efficient Operating Systems
Some advanced operating systems are more than MPS-ready. They are also multiprocessor-
efficient. These operating systems gain maximum advantage from multiple processors.
Windows NT is an example of a multiprocessor-efficient operating system.
Multiprocessor-efficient operating systems reduce the length of the individual functions
contained within their different threads. In an MPS-compliant multiprocessing computer, all
processors share the same local bus and must load the functions they perform over this bus.
By reducing the length of these functions, a multiprocessor-efficient operating system ensures
that no processor is slowed while another processor loads a function over the local bus. This
guarantees that each processor is used to its best advantage.