[j-nsp] RLDRAM sizes of MPC line cards

Saku Ytti saku at ytti.fi
Fri Jan 18 05:25:24 EST 2019

Hey Karl,

RLDRAM was only on first gen trio. 2nd gen was DRAM, 3rd gen is some
JNPR proprietary SERDES connected memory chip called XR2 which I'm not
familiar with at all (I assume closer to HMC/HBM design than RDLRAM)

The size of the chip is not very meaningful unless you also have rough
idea how it's used and how many bytes entry takes. Naive assumptions
do not work, because memory latencies are very very high some creative
population of memory is needed, which yields to poor success with
naive models.

PTX has 1 2GB HMC chip (for lookups, +1 or 2 HMC for packet buffers),
but it certainly does not imply 10x capacity compared to 256MB RLDRAM.

Either test or talk to your account team, it's complex design and
simple model will not transfer across platforms.

On Fri, 18 Jan 2019 at 11:12, Karl Gerhard <karl_gerh at gmx.at> wrote:
> Hello
> is there a list of the RLDRAM sizes of various Juniper line cards to be found somewhere on the internet?
> As far as I understand RLDRAM equals (more or less) FIB size which is incredibly important.
> I'm thinking about buying an MPC2 but I'm not sure how long it will last (compared to an MPC-3D-16X10GE) before I will have to start using stuff like FIB localization.
> For the record, this is an MPC-3D-16X10GE:
> > show chassis fpc detail
> Slot 0 information:
>   State                                 Online
>   Temperature                        32
>   Total CPU DRAM                   2048 MB
>   Total RLDRAM                     1324 MB
>   Total DDR DRAM                   5120 MB
>   Start time:                           2018-01-19 01:21:38 CET
>   Uptime:                               364 days, 8 hours, 36 minutes, 45 seconds
>   Max Power Consumption             440 Watts
> Regards
> Karl
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