[Beowulf] Roadrunner picture

richard.walsh at comcast.net richard.walsh at comcast.net
Thu Jun 12 17:05:09 EDT 2008


Not a expert, but I know a thing or two. The triblade is two CB2 blades
which each hold each two PowerXCell processors in a cc-NUMA arrangement.
They sandwch a LS21 blade that is connected to each through a 16x PCIe to HT
bridge. These three are uni-body constructed.  The CB2s resemble the QS22 blade 
that goes into the IBM BladCenter H chassis.  They are vertical full-height
blades which fit 14 to an enclosure.  The RoadRunner triblade is at least double-wide
and maybe more.  Do not know the measurements.   

The photo confuses me though, because am pretty sure these are vertically racked.
Another thing to note is that programming the triblade is tri-binary ... x86, Power, 
and SPE.  MPI processes are doled out to the Opteron blade.  The PowerXCells
are programmed beneath MPI as SIMD accelrators.  The systems processing
power is largely resident in the PowerXCell (~200 peak Gflops per CB2), the
Opteron only accounts for about 44 teraflops of the total peak performance with is
in the vicinity of 1400 teraflops.  Linpack runs at about 85% efficient on the system
and is running on the SPE only I am pretty sure.  Running Linpack it generates 650
Mflops per watt making it pretty Green I guess ... which is what you would expect
from a DLP engine.  As I recall Blue Gene is about 350 Mflops per watt.  But the
650 number maybe does not count the LS21 power consumption.  Anyway ...

Hope that was useful ... now, can someone tell about the IEEE-754-ness of its eDP


"Making predictions is hard, especially about the future." 

Niels Bohr 


Richard Walsh 
Thrashing River Consulting-- 
5605 Alameda St. 
Shoreview, MN 55126 

Phone #: 612-382-4620

-------------- Original message -------------- 
From: "Peter St. John" <peter.st.john at gmail.com> 


I'm  looking  forward to hearing from our  resident  experts, but meanwhile:  http://en.wikipedia.org/wiki/IBM_Roadrunner exlains the  architecture some. The buzzword is "triblade",  which is 3 blades  (with an extension)  employing two types of processors (AMD Opteron and  IBM Cell) in a hybrid subsystem.  I have  no idea what a single Triblade looks like. The  overallmachine is  then composed of zillions of triblades.  
Wow,imagine a Beowulf of those  (jk :-)

Peter (designing a Beowulf of abaci to fit his current budget)

On Thu, Jun 12, 2008 at 3:45 PM, Bernard Li <bernard at vanhpc.org> wrote:

Hi all:

I am sure most people have seen the following picture for Roadrunner
circulating the Net:


However, they don't look likes blades to me, more like 2U IBM x series
servers.  Perhaps those are the I/O nodes?


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