回覆 : subset of EL/IX for DSPs

[Jwusheng Hu <jshu at cn dot nctu dot edu dot tw>]

Julian Rose <jhrose@dial.pipex.com> writes:

> Hello,
>
> Could anyone point me to info regarding a subset of EL/IX
> or POSIX that targets DSPs? Or if anyone else is thinking
> about this then their suggestions would be welcome. The
> context of the question is the kernel I'm developing, please
> see "http://www.jhrose.dial.pipex.com/dsp_K.htm". Thanks.
>

> Nobody has put any real thought into the requirements of DSPs yet.
> Embedded and real-time systems have proven to be difficult enough to
> pin down. I suspect that DSPs would require a subset of the RT subset
> of EL/IX, perhaps with special schedulers and variations of some
> communications primitives. Whether we need to provide a specific DSP
> subset, or whether this would just be a version of the real-time
> subset I don't really know yet.

> Suggestions and comments about what would be good for DSPs are very
> welcome. This would at least help to ensure that the next version of
> EL/IX is not actively DSP-hostile.
>
> --
> Nick Garnett, eCos Kernel Architect
> Red Hat, Cambridge, UK

It appears that there are two types of requirements here and they are 
related to a fundamental design question: will you design a system 
completely based on DSP? Traditionally, DSP usually acts as a slave 
processor preforming repeated calculations for time-critical algorithms. 
Because of this, DSP chips have very little support of system interface like 
ethernet, LCD etc.., compared with most microcontrollers.

However, when the MIPS of DSP exceeds the needs of algorithm complexity, it 
is quite natural to use the extra MIPS for system interface and a RTOS would 
be very helpful. However, most DSP algorithms must be coded in assembly to 
fully utilize the computational capability, e.g., zero-overhead looping. 
This creates a potential threat to RTOS that full control of the CPU 
resource maynot be possible and users can easily crash the kernel by 
mistake. Hence, unless DSP programmers understand the kernel well, she/he 
may have difficulty using other people's RTOS.

On the other hand, the master-slave structure is still popular when DSP 
takes on the computing role for software radio. For example, TI has a 
DSP+ARM solution that is targeted for portable wireless devices. In this 
case, the need would be how to have a single RTOS that handles both 
processors together and provides a seamless communication interface between 
them.

Jwusheng Hu, Professor
Dept. of Electrical and Control Engineering
Embedded System Design Lab,               http://xlab.cn.nctu.edu.tw
Director, EECS DSP lab, 
                            http://dsp.cn.nctu.edu.tw
Executive Consultant, DigiRose Co Ltd,  http://www.digirose.com