[geeks] Itanium 32 bit performace.... hahahaha

[Charles Shannon Hendrix]

Wed, 10 Dec 2003 @ 13:14 -0800, Francisco Javier Mesa-Martinez said:


> On Wed, 10 Dec 2003, Kevin wrote:
> 
> >
> > I've heard this before, but have never understood it.  What is it
> > about Alphas that requires more RAM than other processors?  My Alpha
> > has 256 and seems to run fine as a file server.
> 
> Alphas before the 21164A were not byte addressable, meaing that you were
> wasting a lot of memory if you just needed to store a byte, since
> depending on the compiler/OS you may be wasting a full word (the original
> design called for a KISS approach). It made the chip very simple, since
> you do not have to deal with unaligned aceesses, and of course cache is
> far simplified. I.e. no need to decode a large offset for a cache line.

Did the DEC compiler around 1996 pack bytes to make it more efficient?

Anyone know how GNU C handles it?

I remember it eating RAM quickly on some projects, and not others.
Maybe it was inconsistent.

There were problems with using a lot of barrier instructions on the
21064 as well.

The later Alphas are so good at preduction, it almost doesn't matter.


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