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Re: standard runtime for (possible/hopeful) 64bit kernels

David Holland wrote:

> On Mon, Mar 16, 2009 at 03:10:11PM +1100, Simon Burge wrote:
>  > > (I'm not currently clear on to what extent
>  > > N32/N64 is coupled to the 64-bit FPU; if it is, we might end up
>  > > wanting the O64 ABI...)
>  > 
>  > I'm not exactly sure what you mean by "64-bit FPU" - do you mean using
>  > all 32 FP regs in 64-bit mode, instead of the 32 FP regs in 32-bit
>  > "paired" mode?
> Yes.
>  > If so, n32 and n64 both use 32 FP regs in 64-bit mode
>  > so both ABIs have the "full" FPU available.
> Right; the (implicit) question is whether you can have N32 without
> that FPU, as e.g. on a mips-II, or whether such machines have to build
> userland, or at least anything using the FPU, as O32 or O64.

n32 is a 64-bit ABI - you _need_ a 64-bit integer MIPS III CPU or
greater (except of course MIPS32).  I'm positively certain that there
are no 64-bit CPUs that only implement the old R3K style 32 x 32-bit

That said, there's some MIPS32 CPUs with a "64-bit" FPU that have the
full 32 64-bit FP regs, but that's a different answer to a question you
didn't ask :-)


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