The new division has been given the name Metagence Technologies. The first product to use its Meta core is the Digital Audio Broadcasting (DAB) receiver chip being developed by Digital One and Imagination, a move announced in mid-April.

The core has been in development for four years and earlier forms have been used in some of Imagination's designs.

Hossein Yassaie, president and CEO of Imagination, said: "We haven't invented this overnight.

"The reason for doing a multithreaded design is because of the devices that are coming. They will be mobile devices that need to do multiple functions in realtime. More devices will have to handle multimedia and baseband processing [at the same time]."

He said that a multiprocessing approach would demand more on-chip resources and increase power consumption. Multithreading, in which the processors dynamically switches between program threads on a cycle by cycle basis, is more efficient, claimed Yossaie.

Intel has employed multithreading in the microcode engines in its IXP processors and Sun Microsystems plans to use it in the Java-oriented Majc processor. Infineon Technologies has said multithreading is a possible evolution for the TriCore architecture.

The primary advantage of multithreading is that it can hide memory latency. In the case of the Intel IXP microengines, the processor core switches to another thread whenever the running thread needs to fetch data from memory. Because that thread has to wait for the data, the processor switches to any thread that has data ready to process. This fine-grained switching effectively removes much of the effect of memory latency on processing throughput.

"Latency is a very important issue when you do system-on-chip. You may have five different on-chip components. While one is accessing memory, the other four have to wait," said Yossaie.

Yossaie said the company has adopted a more advanced approach to multithreading. Instead of switching on a pure round-robin basis, the core takes account of the priorities of threads that are ready to run, helping to meet realtime deadlines.

"There are two levels of multithreading. At one level, the programmer has total control to define how things happen," said Yassaie.

"But we have added a new technology, called AMA, automatic MIPS allocation. It lets you compartmentalise a thread in a virtual processor."

Under AMA, Yassaie said threads have their own MIPS requirements that can be expressed to the core, together with their realtime constraints, such as deadlines. There are five or six parameters that the application sets.

"Integration is very simple when you bring software under this control mechanism," said Yossaie.

"It is a hardware engine. There is no software overhead for anything."

The processor calculates its current workload so that it can reject tasks that would overload it.

When running, each thread has full access to all of the execution units in the core to improve support for time-critical broadband processing functions, said Yossaie.

"It can do things like an FFT [fast Fourier transform] in a couple of cycles. We are not just depending on multithreading for performance. We have a very strong architecture."

Metagence has designed Meta to scale in terms of execution units, such as multiply-accumulate engines, and there will be a level of configurability that licensees can use.

"Licensees can have special instructions. However, there needs to be some compatibility so we are a bit more rigid than some," said Yossaie.

"It's a formal architecture. We are not sticking a few ALUs [arithmetic logic units] here and there."

Metagence will sell the Meta cores using a standard licence fee plus royalty model. Compilers, assemblers and linkers are being developed by the company's Ensigma division but Imagination is also talking to third-party tools suppliers.

"We are talking to a number of semiconductor companies and system companies," said Yassaie.

The core will be made available in both soft and hard forms.

The Metagence division has 30 people in it and Imagination is still recruiting for the division as well as Imagination.

"We are growing at the speed of lightning. Imagination as a group has a target of growing at 10 to 20% a year," said Yossaie.