[Gems-users] crossbar

["Mladen Nikitovic" <mladen@xxxxxxxxxxx>]

Hi,

I would like to have a better understanding of the crossbar model using the
MSI_MOSI_CMP_directory protocol. I did a simulation with 4
processor-configuration.

Firstly, under "Network Configuration" it states that the network is a
SIMPLE_NETWORK and that the topology is a CROSSBAR. However, a number of
virtual_net_0/1/2/3/4 are mentioned that are either ordered or unordered.
Could you give a brief explanation of what this is and why some are ordered
and others unordered? What does it mean that a virtual_net is
ordered/unordered? 

Secondly, statistics show (under "Network stats") utilization for switch_0
until switch_12, so there are 13 (0 until 12) switches in total. It seems
like there is one top-switch (Nr 12) that all are connected to, right? Does
this mean that there is a hierarchy? I fail to understand how these switches
are organized from a topology point of view. Is 13 switches really needed to
connect 4 processors and L2? If yes, could you explain how they are
used/connected?

A final side note, I saw that the final four data from the last switch only
specified Control stats, whereas the rest of the switches had both Data and
Control. Is there a reason for this?

Hope you can shed some light on this matter.

Regards,
Mladen

Mladen Nikitovic
PhD student in Adaptive CMPs

Royal Institute of Technology (KTH)
Department of Microelectronics and Information Technology (IMIT)