Re: [Gems-users] Meaning of the 'Directory' in memory system

[Muhammad abid Mughal <mabidm_pieas@xxxxxxxxx>]

1, Each chip can have any number of L1$,L2$ and memory i.e. Directory.The number of L1$ is always equal to number of processors per chip.

2.Ruby combines memory and memory coherence in to a single entity called Directory.Each entry in a directory can have data,coherence states,etc , in 

    general. Please see protocols folder in gems-2.1

3.g_NUM_MEMORIES means number of directories.

  

    most of the protocols don't  simulate memory in detail i.e. they don't use "MemoryControl" class.They just use MEMORY_LATENCY parameter to provide memory read latency.Some protocols do use "MemoryControl" for detailed memory simulation. use grep in "protocols" folder.

Regards,

Muhammad abid

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From: Woomin Hwang <wmhwang@xxxxxxxxxxxxxxxx>
To: gems-users@xxxxxxxxxxx
Sent: Thursday, December 2, 2010 10:00:35
Subject: [Gems-users] Meaning of the 'Directory' in memory system

Hello, everyone.

 

I’m working with ruby to instantiate additional memory module with different access timing.

Currently I’m analyzing structure of memory system. But I’m very confused.

What I understand is that: physically, a DIMM can have several chips, and a chip can have several banks (BANKS_PER_RANK).

A chip can includes cache controllers, cache objects, DirectoryMemory objects, etc.

It’s hard for me to map each objects to the physical structure.

 

Please explain about the mapping of objects and physical components, and additionally :

 

1.     Does a ‘chip’ includes a processor, L1 & L2 caches, and memory DIMMs? Or is it just a single component such as single memory chip?

2.     What is the exact meaning of the ‘Directory’ in the memory system? Does it represent a memory bank or whole banks in a chip?

3.     What is the meaning of the param g_NUM_MEMORIES? I guess the parameter represents the number of ‘Directory’ in the memory system, but don’t know exactly.

 

Please help me.

 

Thank you

 

 

Regards,

Woomin Hwang