Hello,

Paul referred to gem5 not being able to put backpressure on the CPU from the 
main memory, citing this topic;

> http://www.mail-archive.com/gem5-users@gem5.org/msg03792.html

According to this post there is no limit to the number of concurrent page 
walks.  Do page walks go through the main memory system and could reach DRAM by 
the normal mechanisms?  Is it a true statement about lack of backpressure?  It 
seems hard to believe because response latency is being modeled.

Thanks

Dave


On Oct 23, 2012, at 12:49 PM, Paul Rosenfeld wrote:

> As someone who has used (and tried to modify) both marssx86 and gem5, I would 
> like to add one (potential) benefit to the marssx86 side of things: the 
> emulation mode (via QEMU) allows you to boot the system very quickly up to a 
> region of interest and take a checkpoint right before the simulation launch 
> point. From what I understand, the full system boot process is much slower in 
> gem5 even if booting with a simple CPU model and then picking up with the O3 
> model. 
> 
> Additionally, since you mentioned DRAMSim2, it might be worthwhile to note 
> that even with DRAMSim2, gem5 does not (currently) support putting 
> backpressure on the CPU (see: 
> http://www.mail-archive.com/gem5-users@gem5.org/msg03792.html), which, 
> depending on what you're trying to do, this may or may not be an important 
> consideration. 
> 
> Finally, one last thing to add to your list, marss doesn't support any kind 
> of syscall emulation mode (i.e. you have to run full system mode all the 
> time) whereas gem5 does. 
> 
> -Paul
> 
> On Mon, Oct 22, 2012 at 5:06 PM, Payne, Benjamin <bpa...@lps.umd.edu> wrote:
> Hello,
> 
>  
> 
> What is the difference between gem5
> 
> http://gem5.org/Main_Page
> 
> and MARSS (Micro-ARchitectural and System Simulator for x86-based Systems)
> 
> http://marss86.org/~marss86/index.php/Home
> 
>  
> 
> As far as I can tell,
> 
> -gem5 can support Alpha, ARM, SPARC, and x86 instruction set architectures, 
> whereas MARSS is only for x86.
> 
> -gem5 can be integrated into Structural Simulation Toolkit, whereas MARSS has 
> not been
> 
> -both gem5 and MARSS can simulate multiple cores
> 
> -both gem5 and MARSS can use DRAMSim2
> 
>  
> 
> Please correct me if any of these statements are incorrect.
> 
>  
> 
> Are there any other considerations?
> 
>  
> 
> Thank you,
> 
>  
> 
>  
> 
> Ben Payne
> 
> http://mst.edu/~bhpxc9/
> 
> Suite 450, Room S452
> 
> 5520 Research Park Drive
> 
> Catonsville, MD 21228-4870
> 
> Laboratory for Physical Sciences
> 
> http://www.lps.umd.edu/
> 
> office: 443-654-7890
> 
> cell: 608-308-2413
> 
>  
> 
> 
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