[ECOS] [Fwd: Re: [ECOS] IDT MIPS support]

[ECOS] [Fwd: Re: [ECOS] IDT MIPS support]

[Michael Rapoport]

Hello,

I'd like to clarify the following:
1. What does it mean - 

"the NEC VR4300 is an implementation of
the 64-bit R4000 architecture (although the eCos port only uses it in
32-bit mode)"

If I understand correctly, the available port is done only for the 32-bit
mode of the MIPS CPU.

If we need the 64-bit implementation in the eCos, compiler and debugger -
what should we do ???

We are very new to the eCos and free s/w - every piece of information will
be appreciated.

Thank you very much,
Michael Rapoport.



>-------- Original Message --------
>Subject: Re: [ECOS] IDT MIPS support
>Date: Mon, 7 Aug 2000 13:04:27 +0100
>From: Bart Veer <bartv@redhat.com>
>Reply-To: bartv@redhat.com
>To: uri_s@rad.co.il
>CC: ecos-discuss@sources.redhat.com
>References: < 398DAF68.45507EFC@rad.co.il >
>
>>>>>> "Uri" == Uri Shabi <uri_s@rad.co.il> writes:
>
>    Uri> I'm considering to use ecos with IDT MIPS 64474/5 , Does
>    Uri> anyone is implementing/aware of such support.
>
>I am not aware of any ports in progress to this MIPS variant.
>
>    Uri> If this is not available can anyone comment on modifing other
>    Uri> MIPS (NEC/Toshiba) to support the IDT?
>
>I have not looked at the IDT parts. The TX39 is an implementation of
>the 32-bit R3000 architecture, the NEC VR4300 is an implementation of
>the 64-bit R4000 architecture (although the eCos port only uses it in
>32-bit mode), so two of the main MIPS variants are already covered.
>If the IDT part corresponds to one of these then a port should be
>fairly straightforward.
>
>There is no MIPS16 or 64-bit support in eCos yet, nor any port to a
>MIPS IV implementation. If you need any of these then a port would
>involve significantly more effort.
>
>You also need to take into account the effort that will be needed for
>a board port to whatever hardware you intend to use, plus any device
>drivers that may be needed.
>
>Bart Veer // eCos net maintainer
>
=============================================
  Michael Rapoport                          | TEL:  +972 3 6455432
  RAD Data Communications Ltd.     | FAX:  +972 3 6455305
  31 HaBarzel Str. Tel Aviv,               | e-mail:
  69710  Israel                                 | michael_r@rad.co.il
=============================================

Re: [ECOS] [Fwd: Re: [ECOS] IDT MIPS support]

[Bart Veer]

>>>>> "Michael" == Michael Rapoport <michael_r@rad.co.il> writes:

    Michael> Hello,
    Michael> I'd like to clarify the following:
    Michael> 1. What does it mean - 

    Michael> "the NEC VR4300 is an implementation of the 64-bit R4000
    Michael> architecture (although the eCos port only uses it in
    Michael> 32-bit mode)"

    Michael> If I understand correctly, the available port is done
    Michael> only for the 32-bit mode of the MIPS CPU.

Correct. Specifically eCos is compiled with -mgp32, so the compiler
assumes that 32 32-bit general purpose registers are available. The
fact that the registers are actually 64 bits is ignored. On a context
switch only 32 bits per register are saved. Etc. Offhand I am not
quite sure how eCos handles the floating point registers on the
VR4300. 

    Michael> If we need the 64-bit implementation in the eCos,
    Michael> compiler and debugger - what should we do ???

In theory the compiler and debugger are OK for 64-bit, but since so
far no paying customer has funded a 64-bit eCos port the eCos team has
not validated this assumption.

If you look at e.g. the MIPS hal_arch.h header file you will see that
there is some support in there already for running in 64-bit mode,
but it will not have been exercised heavily if at all. Generally you
will need to read up about the eCos HAL (see the Reference Guide), and
have a good look at the various MIPS HAL packages.

Hopefully all other eCos packages will just work when running in 64
bit mode, but again this has not been tested. It is possible that
there are various nasty bugs just waiting to trigger. The only way to
find out is to try it and see.

Bart Veer // eCos net maintainer