[mvapich-discuss] MVAPICH2 Performance Evaluation

[Amit H Kumar]

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