[ECOS] Re: eCos on 80186

Grant Edwards grante@visi.com
Wed Mar 30 19:13:00 GMT 2005


In gmane.os.ecos.general, you wrote:
>>>>>> "Grant" == Grant Edwards <grante@visi.com> writes:
>
>    Grant> As a purely academic question, what is the "smallest"
>    Grant> processor/platform to which eCos has been ported? There are
>    Grant> some fairly "wimpy" processors with gcc support (e.g. 6811,
>    Grant> AVR), but they tend to have rather limited address spaces
>    Grant> by eCos standards.
>
> Obviously this depends on the definition of "smallest".
>
> I have RedBoot running on an old vanilla 68000, but haven't finished
> the eCos side yet. In terms of transistor count I suspect that is the
> smallest - obviously the lack of on-chip peripherals helps.
>
> Anoncvs has support for h8300 and calmrisc16 (the latter
> RedBoot-only IIRC). From a computer science/architecture
> perspective I suspect one of those two would qualify as
> "smallest".

The H8/300H is a 32-bit CISC processor a 24-bit linear address
space. I don't really consider it "small" from an embedded OS
POV.

CalmRISC seems to be more what I hand in mind. It has a 20 bit
program address space and a 16 bit data address space.

> For practical hardware design purposes I suspect the LPC2xxx
> ARM chips currently qualify as smallest.

I was thinking more along the lines of address space and ALU
width (e.g. something like the 6811 with an 8/16 bit ALU and 16
bit linear address space).  I can see how you might be able to
shoehorn a stripped down eCos[1] into a harvard architecture
with two 16-bit address spaces, but a single 16-bit address
space doesn't sound practical.

[1] A minimal multi-tasking kernel with a few services like
    mutexes and semaphores.  A BSD network stack is obviously
    out of the question.

-- 
Grant Edwards                   grante             Yow!  I feel like I'm
                                  at               in a Toilet Bowl with a
                               visi.com            thumbtack in my forehead!!

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