[j-nsp] understand the DRAM usage on CFEB(FEB-M10i-M7i-S)

[Martin T]

Ok, thanks! I had never seen a solution where parity information is
stored in additional individual SDRAM chips. So in conclusion 128MiB
of on-board SDRAM is used for packet memory, 64MiB of on-board SDRAM
is used for packet memory parity information and replaceable DDR SDRAM
SODIMM is used solely for the PFE microkernel.


regards,
Martin

On 9/29/15, Michael Loftis <mloftis at wgops.com> wrote:
> The "extra" SDRAM chips.  The packet memory has parity or ECC bits, I
> actually do not recall for sure which, but the "extra" is for those
> extra bits.
>
> On Tue, Sep 29, 2015 at 12:45 PM, Martin T <m4rtntns at gmail.com> wrote:
>> What do you mean?
>>
>>
>> thanks,
>> Martin
>>
>> On Tue, Sep 29, 2015 at 8:45 PM, Michael Loftis <mloftis at wgops.com>
>> wrote:
>>> Parity/ECC.
>>>
>>> On Tue, Sep 29, 2015 at 7:32 AM, Martin T <m4rtntns at gmail.com> wrote:
>>>> Hi,
>>>>
>>>> according to Juniper M10i Compact Forwarding Engine
>>>> Board(http://www.juniper.net/techpubs/en_US/release-independent/junos/topics/concept/cfeb-m10i-description.html)
>>>> documentation it has 128 MiB SDRAM for packet memory and 128 MiB SDRAM
>>>> for the microkernel. If I visually inspect the CFEB, then it has
>>>> twelve "MT 46V8M16" DDR SDRAM chips which means 12x 134217728 bits,
>>>> i.e. 192MiB of on-board soldered DDR SDRAM. Questions:
>>>>
>>>> 1) Are four "MT 46V8M16" DDR SDRAM chips actually not in use? If they
>>>> are in use, then what for?
>>>>
>>>> 2) Am I correct that on-board soldered DRAM is used for shared packet
>>>> buffer and installable DDR SDRAM SODIMM is used for the microkernel?
>>>>
>>>>
>>>> thanks,
>>>> Martin
>>>> _______________________________________________
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>>>
>>>
>>>
>>> --
>>>
>>> "Genius might be described as a supreme capacity for getting its
>>> possessors
>>> into trouble of all kinds."
>>> -- Samuel Butler
>
>
>
> --
>
> "Genius might be described as a supreme capacity for getting its possessors
> into trouble of all kinds."
> -- Samuel Butler
>