Re: 64-bit and N32 kernel interfaces

[Hartvig Ekner <hartvige@mips.com>]

Maciej W. Rozycki writes:
> 
> On Thu, 5 Sep 2002, Daniel Jacobowitz wrote:
> 
> > No - the point is that all data types have the same size in N32.  It
> > was created explicitly as a transitional sop for people who didn't want
> > to fix their code, but wanted a performance increase from their 64-bit
> > hardware.
> 
>  Well, what's the performance increase of n32 over o32?  The increased
> number of argument registers?  I doubt it's noticeable in most cases.

The technical benefits of n32 over o32 are:

* More argument registers => less memory traffic, less D-cache use,
        => faster code

* 64-bit datapath of CPU can be utilized with big impact on certain
  applications

* 32 floating point registers instead of 16 (and more efficient
  parameter passing as well)

/Hartvig