[Gems-users] Crossbar with SimpleNetwork

[Joseph Pusdesris <joemp@xxxxxxxxx>]

Hello, I am trying to generate several topologies for the M5 simulator using Ruby's SimpleNetwork and I have a few questions.  Am I correct in assuming that the SimpleNetwork framework cannot support a bus model without modifying the source for PerfectSwitch?  

 

I am also confused about the topologies which are included in the repository.  The default crossbar topology that is included in the m5 repository generates something along these lines:

 

ext_node:L1Cache:0 int_node:0 link_latency:1 bw_multiplier:64

ext_node:L1Cache:1 int_node:1 link_latency:1 bw_multiplier:64

ext_node:L1Cache:2 int_node:2 link_latency:1 bw_multiplier:64

ext_node:L1Cache:3 int_node:3 link_latency:1 bw_multiplier:64

ext_node:L2Cache:0 int_node:4 link_latency:1 bw_multiplier:64

ext_node:Directory:0 int_node:5 link_latency:40 bw_multiplier:10

 

int_node:0 int_node:6 link_latency:40 bw_multiplier:16

int_node:1 int_node:6 link_latency:40 bw_multiplier:16

int_node:2 int_node:6 link_latency:40 bw_multiplier:16

int_node:3 int_node:6 link_latency:40 bw_multiplier:16

int_node:4 int_node:6 link_latency:40 bw_multiplier:16

int_node:5 int_node:6 link_latency:40 bw_multiplier:16

 

This doesn't make sense to me.  Why is there the extra level of switches before connecting nodes to the xbar switch?  Is it an error in the repository or am I misunderstanding something?  Wouldn't a more proper crossbar look like:

 

ext_node:L1Cache:0 int_node:0 link_latency:1 bw_multiplier:64

ext_node:L1Cache:1 int_node:0 link_latency:1 bw_multiplier:64

ext_node:L1Cache:2 int_node:0 link_latency:1 bw_multiplier:64

ext_node:L1Cache:3 int_node:0 link_latency:1 bw_multiplier:64

ext_node:L2Cache:0 int_node:0 link_latency:1 bw_multiplier:64

ext_node:Directory:0 int_node:0 link_latency:40 bw_multiplier:10

 

-Joseph