Re: Doom 3 performace as a 64-bit game (theoretically)

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2005/10/25, Jonathan Berry <berryja@xxxxxxxxx>:
> On 10/22/05, Kenneth Porter <shiva@xxxxxxxxxxxxxxx> wrote:
> > --On Saturday, October 22, 2005 1:15 AM -0500 Jonathan Berry
> > <berryja@xxxxxxxxx> wrote:
> >
> > > "64 bit is not going to speed up Doom 3. In fact there may actually be
> > > a minor slowdown since the pointer references are all in 32 bit, which
> > > will mean a hit to memory bandwidth which is the real gating problem."
> > >
> > > What does "pointer references are all in 32-bit" mean?  You can
> > > address more virtual memory in 64-bit, which usually means that memory
> > > intensive programs do better.
> >
> > Pointers will be 64-bit, which means that instructions that need to load
> > pointers will touch more memory. Indirection gets more expensive. Without
> > the greater number of registers that came with AMD64, that might have
> > inflicted a noticeable performance penalty on his engine. Gamers tend to
> > obsess over small improvements that programmers consider negligible, so
> > that would have marketing consequences.
>
> Perhaps this is what he meant.  Though, let's not forget a DDR memory
> interface is 64- or 128-bits wide.  I don't think it will take any
> longer to get a 64-bit pointer than a 32-bit one.  Right?  You get at
> least 64-bits per (FSB) cycle.  I still go back to it was an old quote
> and maybe doesn't apply anymore.  I cannot see any slight memory
> overhead outweighing the other benefits of x86_64.
>
> Jonathan
>
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feel free to prove me wrong with the quake3 code ;).

regards,
rudolf kastl


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