Re: [Gems-users] Cache Organization

[Niket Agarwal <niketa@xxxxxxxxxxxxx>]

The g_FLIT_SIZE is a GARNET specific parameter and GARNET does not use  
the g_endpoint_bandwidth and bw_multiplier arguments.
g_FLIT_SIZE is used to specify the bandwidth (bytes/cycle) of on-chip  
links. It was chosen assuming constant on-chip link latency. If there  
is a desire to have different link bandwidths, the latencies in the  
topology file can be increased to incorporate that. For e.g. if a link  
with half the bandwidth of g_FLIT_SIZE is desired, the latency for the  
link can be doubled. So, if the g_FLIT_SIZE is 16 bytes/cycle and a  
link of 8 bytes/cycle is desired, the latency of the particular link  
can be made to 2. So, 16 bytes will take 2 cycles to cross the link =  
8 bytes/cycle. I think the pipelining in that particular link would  
have to be removed. Currently GARNET assumes that if a link has a  
latency >  1, there can be multiple flits on the link at a time.
As regards the L2 cache organization, from my understanding, L2 on a  
"chip" is always shared. So, if you define multiple L2's on a chip the  
L2 would be banked but would still be shared. The only way to get  
private L2 is to have multiple "chips"
-Niket

On Oct 16, 2008, at 10:43 AM, hb166307@xxxxxxxx wrote:

> Dear Users,
>
>    I have been reading through the archives trying to understand how  
> the cache
> structure is organized and have come across information that leads  
> me to believe
> that if I place one L2Bank on a "chip" or a CMP in a Multiple-CMP  
> system that it
> is considered shared; and if I place more than one on a "chip" each is
> considered private or is there more to it than that?
>
>    My next question is in regard to the g_endpoint_bandwith  
> parameter versus
> g_FLIT_SIZE:
>
>     1) g_FLIT_SIZE determines the amount of bytes/cycle across all  
> links?
>     2) g_endpoint_bandwidth allows me to increase the bandwidth of  
> individual
>        links when specified in a custom network design?
>     3) So If I have g_FLIT_SIZE as 16, but my bw_multiplier = 64
>        and g_endpoint_bandwidth = 1000 what is the bandwidth on the  
> specified ink
>        versus the others.
>
> I would appreciate any help trying to figure this out.
>
> Thanks
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