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_lior_
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PostPosted: Sat Dec 24, 2005 11:37 am    Post subject: Endianess on MIPS? Reply with quote

is it possible to switch the endian format via software on MIPS? I would like to have a little-endian running Octane or Indy to develop and port some little piece of apps for a Xilleon target which has a 4kc little-endian embedded core.

cross compiling sometimes sucks!
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drwook
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PostPosted: Sat Dec 24, 2005 1:35 pm    Post subject: Reply with quote

AFAIK no I'm afraid.

What about running under an emulator for a little endian arch though?
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_lior_
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PostPosted: Sat Dec 24, 2005 11:06 pm    Post subject: Reply with quote

emulators are worst than cross compiling.
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Redhatter
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PostPosted: Sun Dec 25, 2005 12:12 pm    Post subject: Reply with quote

Afraid not... otherwise I would have a nice mipsel userland sitting on iluxa's IP27 to do stage builds on. :-)

Endianness is decided by the wriing of the CPU to the memory banks and other devices, not by registers alone.
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drwook
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PostPosted: Mon Dec 26, 2005 9:45 am    Post subject: Reply with quote

Indeedy.

Just wondering what the problems you're having cross-compiling though?

& what the problem with emulation is, other than loss of performance?
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Redhatter
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PostPosted: Mon Dec 26, 2005 1:11 pm    Post subject: Reply with quote

Cross compiling a userland requires all sorts of voodoo. Believe me, I've tried. :-)

Emulation isn't bad when it works well... and after all, the boxes we're using aren't particularly fast. (My Qube2 runs at a whopping 250MHz, and has no secondary cache) But most emulators I've seen bearly break the 100MHz mark emulating a MIPS on a modern x86 system.
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Kumba
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PostPosted: Fri Jan 06, 2006 6:05 am    Post subject: Reply with quote

SGI Systems are explicitly hardwired to Big Endian. Some of the newer MIPS Technologies development boards, and those out of AMD and Broadcom can switch endianess by uploading a new firmware into the flash memory and flipping a jumper, I believe. But such boards are extremely rare, and thus, none of us have any of them in our possession to tinker with.


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GNUtoo
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PostPosted: Sat Jan 14, 2006 3:46 am    Post subject: Reply with quote

and how do you do this on a G4 (powerpc) ?
they are bi-endian
by defaault they are big-endian on apple machines
that would be interesting...
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Redhatter
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PostPosted: Sat Jan 14, 2006 4:06 am    Post subject: Reply with quote

G4s probably have a hardware switch like MIPS. In any case, you'd need new firmware and OS to cope with the little endian CPU, it can't be done purely in software.
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GNUtoo
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PostPosted: Sun Jan 15, 2006 12:08 am    Post subject: Reply with quote

too bad
now i understand why this is a problem for darwine...
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Blood Fluke
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PostPosted: Thu Feb 02, 2006 6:05 am    Post subject: Reply with quote

Redhatter wrote:
But most emulators I've seen bearly break the 100MHz mark emulating a MIPS on a modern x86 system.

Most MIPS chips barely break the 100 MHz mark :P Also, MIPSel emulation is really pretty decent these days. e.g. Gxemul or Simics

Gxemul primarily does DEC-MIPS emulation. Not all that useful for emulating your embedded target boards. It handles some other stuff, too, but the DEC-MIPS emulation is the most highly developed piece.

Virtutech Simics simulates the MIPS Malta eval board and a variety of processors. It's free for non-commercial use. (With the exception of research projects. Non-research academic use is fine under the free license, though.) I would expect that porting linux as a hobby qualifies for the free license :)

(Simics does a lot of other architectures and other stuff, but MIPS emulation is what's relevant to this thread...)
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