[mvapich-discuss] MVAPICH2 Performance Evaluation

[Eric A. Borisch]

Amit,

Is your PCI-X bus possibly at 100MHz and not 133? If there is
something else sharing the PCI-X bus, it may be at the lower rate.

 Eric

On 10/12/06, Amit H Kumar <AHKumar at odu.edu> wrote:
> Thank you Greg for your simple  explaination. ...
>
> mvapich-discuss-bounces at cse.ohio-state.edu wrote on 10/10/2006 11:29:43 PM:
>
> > On Tue, Oct 10, 2006 at 11:09:19PM -0400, Amit H Kumar wrote:
> >
> > > Just Curious, Since the switch that we have is InfinIO 3000 (a speed of
> > > 10Gbps = 1.16GBytes/s ).
> >
> > The link speed for IB is quoted as 10 Gbps, but after 10b/8b encoding
> > the actual data rate is 8 Gbps, e.g. 8 x 10^9 bit/s. So that's 1 Gbyte/s
> > (where giga = 10^9) or 0.931 Gbyte/s (where giga = 2^30).
>
> I wouldn't have known about 10b/8b encoding. Now, I know it :)
> Atleast this tells me what to really expect.
>
> >
> > Not that this answers your question ;-) but it's worth mentioning as
> > lots of people don't know it.
>
> The question that remains unanswered:
>  The bandwidth that the tests show is 613 MBytes/s uni-directional, & 813
> MBytes/s bi-directional.
>  As per the above explaination I should be expecting close to a "Giga Byte"
> in One direction.
> Could it be something that I am doing wrong, or the limitations of the
> PCI-X?
>
> Can any one please comment on this?
>
> Thank you,
> Amit
>
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-- 
Eric A. Borisch
eborisch at ieee.org