AMD vs Intel memory managemement

[Nadim Hoque]

If i recall AMD started doing NUMA which each core gets a dedicated amount
of memory that is tied to it. The plus side is that when the core needs
something in its own memory region it does not need to put the request in
the queue like in non-numa and gets it faster. The down side is if it needs
data in a memory region that belongs to another core it will take longer
since it essentially has to ask that core for that data. In non-numa
architecture the entire memory space is allocated to all cores which means
that each core can access memory with out asking another for data. The
problem with this is that all memory requests is put in a queue and the
core has to wait until the memory controller is able to process the
request.  For many core and lot of memory systems you are mostly better off
with NUMA. Correct me if I am wrong though.


On Mon, Jun 3, 2013 at 7:25 AM, Stephen <cryptworks at gmail.com> wrote:

> Not really, Dual channel mode means you can read and write to both Banks
> of memory at the same time (aka Ganged). Single Channel means you treat all
> ram as a single bank reading and writing to one and then the other. think
> Raid 0 vs JBOD if that helps.
>
> I personally have had 0 issue with greater than 4 GB of ram in a machine
> with Linux and a 64 bit kernel. and i have worked with multiple
> distributions over the years back and forth.
>
> the main difference between Intel and AMD i have seen since the core i
> series CPUs were released is that AMD still has wicked fast memory
> performance but Intel wins most everything else.
>
> If you have multiple processors you will want to look for numa. This
> allows inter processor communication for ram access.
>
> It should not matter if you are running ganged or unchanged your is should
> see all ram installed with the exception of the PCI/pcie/chip set nibbling
> 100 to 700mb for doing its thing in consumer chipsets.
>  On Mon, Jun 3, 2013 at 6:36 AM, keith smith <klsmith2020 at yahoo.com>wrote:
>
>>
>> I found this in an on-line discussion:
>>
>> Ganged = dual channel mode for ram. All cores get access to 100% of the
>> ram.
>>
>> unganged = single channel. Each core gets access to a stick of ram.
>>
>> Is this correct?
>>
>>
>> ------------------------
>> Keith Smith
>>
>> --- On *Mon, 6/3/13, Nathan England <nathan at nmecs.com>* wrote:
>>
>>
>> From: Nathan England <nathan at nmecs.com>
>> Subject: Re: AMD vs Intel memory managemement
>> To: "Main PLUG discussion list" <plug-discuss at lists.phxlinux.org>
>> Date: Monday, June 3, 2013, 1:35 AM
>>
>>
>>
>>
>>
>>
>> Yeah, it's a wonderful thing AMD calls "unganged" mode. I have 8 GB of
>> ram in my server and the motherboard has enabled "unganged" mode to be more
>> efficient. CentOS only recognizes 5.8 GB of ram and I cannot turn off
>> unganged mode.
>>
>>
>>
>> I love it...
>>
>>
>>
>> </sarcasm>
>>
>>
>>
>>
>> On Sunday, June 02, 2013 17:46:19 keith smith wrote:
>>
>>
>>
>>
>> Hi,
>>
>> After that great thread on 32bit vs 64bit, I was wondering if it would be
>> beneficial at this point to drill down to the CPU level : AMD vs Intel.
>>
>> We had a great thread a while ago the AMD CPU, however I do not think
>> that thread covered memory management.
>>
>> I almost went for an AMD CPU this go around (I have a couple from prior
>> purchases), however after hearing that AMD does some weird memory
>> management at the core level, assigning memory by the bank to each core, I
>> thought I would go with an Intel CPU.
>>
>> If I understand this correctly, It sounds like under some or most
>> circumstances the server will lose a portion of the total memory because
>> under AMD RAM is assigned at the core level and bank level.  I assume Intel
>> uses memory as a pool.  Need memory just grab some until it is gone.
>>
>> Any thoughts on this?
>>
>> Thanks!
>>
>> ------------------------
>> Keith Smith
>>
>>
>>
>> --
>>
>>
>>
>>
>>
>>
>>
>> Regards,
>>
>>
>>
>> Nathan England
>>
>>
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> NME Computer Services http://www.nmecs.com
>>
>> Nathan England (nathan at nmecs.com)
>>
>> Systems Administration / Web Application Development
>>
>> Information Security Consulting
>>
>> (480) 559.9681
>>
>>
>>
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>
>
>
> --
> A mouse trap, placed on top of your alarm clock, will prevent you from
> rolling over and going back to sleep after you hit the snooze button.
>
> Stephen
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-- 
Nadim Hoque
Systems Support Analyst
Engineering Technical Services
Arizona State University
Cell: 480-518-6235
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