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Increasingly, companies are relying on their executive
blogs as a way of communicating with the outside world rather than the
more traditional means of using public relations channels and relying
on the interested media outlets to provide coverage. And so it is that
we learn from the blog of Jonathan Schwartz, Sun Microsystems' chief executive officer, that the company has received first silicon on its future "Rock" multicore Sparc processor.
The chip that Schwartz has in a baggie on his desk, which is shown
below, is actually named the UltraSparc RK. This particular chip is a
dud that doesn't work--which is what happens when you first implement a
chip in silicon; you get some duds that you can use for PR purposes as
the few good ones you get end up in alpha systems to test software.
Increasingly, companies are relying on their executive
blogs as a way of communicating with the outside world rather than the
more traditional means of using public relations channels and relying
on the interested media outlets to provide coverage. And so it is that
we learn from the blog of Jonathan Schwartz, Sun Microsystems' chief executive officer, that the company has received first silicon on its future "Rock" multicore Sparc processor.
The chip that Schwartz has in a baggie on his desk, which is shown
below, is actually named the UltraSparc RK. This particular chip is a
dud that doesn't work--which is what happens when you first implement a
chip in silicon; you get some duds that you can use for PR purposes as
the few good ones you get end up in alpha systems to test software.
The Rock chip has a total of 2,395 pins, and according to Schwartz,
there are 812 pins that feed into the Rock cores and another 1514 pins
are used for power and grounding. That leaves another 69 pins that are
not yet connected to anything, and it is interesting to ponder what
other things Sun will eventually cram onto the Rock chip as the chip
evolves and chip fabrication processes allow the electronic components
in the chip to be shrunk. As we previously reported, the Rock chip will
have 16 Sparc cores, and Schwartz added another piece to the puzzle in
his blog by saying that the Rock chip will be able to support 256 TB of
memory in a coherent manner. Top-end RISC/Unix and X64 servers are
stretching to hit 2 TB these days.
"That is an awful lot of RAM in a single system (and given the cost of
memory nowadays, you'd want to post an armed guard next to that
machine)," Schwartz quipped.
Sun has not said how many Rock processors it will gang up in its future
"Supernova" servers when these boxes start shipping next year. Sun has
not said how many threads each Rock core will have or what their clock
speeds will be, but the company did say back in early February
that a top-end Rock machine would have 16 times the performance of a
Sun Fire E25K server using the dual-core UltraSparc-IV+ processors.
That E25K machine has 144 cores in total spread across 18 four-socket
system boards. Each system board can support up to 64 GB main memory
using 2 GB DDR2 DIMMs, for a maximum main memory of 1.15 TB. That works
out to 8 DIMM slots per CPU socket, or 4 DIMM slots per core in the
E25K. The UltraSparc-IV+ chips are interconnected with the 150 MHz
Sunplane interconnect, which provides NUMA/SMP clustering to give
Solaris a single system image to play with.
Back in February, Sun reconfirmed that it was on track to deliver the
Rock processors in the second half of 2008. It has not said much about
the Supernova systems, but it seems likely that Sun will use a uniboard
design as it did with the past Sun Fire product lines. But Rock
machines may look a lot more like the high-end "Galaxy" X4600 servers,
which are based on AMD's
Opteron Rev E and Rev F processors. In the X4600, a single processor,
its main memory, and its interconnect are all put on a single board
rather than on a board with four sockets. (This is a hunch, not any
inside dope.) But, Sun could also deliver uniboards with two, four, and
eight sockets, too. That would put from two to eight Rock chips in a
box, which works out to 32 to 128 cores using 16-core chips; Sun will
almost certainly have Rock chips with four, eight, and 12 cores
activated, thereby recycling chips that have some dud cores that it
would otherwise throw out. Whether Sun uses single-socket uniboards or
more standard uniboards with multiple sockets is unclear. What does
seem clear is that Sun will probably not go beyond 256 threads in the
biggest system, which means Rock is a 16-core, 32 thread processor.
Future Rock designs and future Solaris releases will almost certainly
support more threads. And that is probably what those extra pins are
all about.
So how is Sun going to get 16 times the performance of the current crop
of generally available Sun Fire 25K systems? Well, just moving to 65
nanometer processes should have allowed the Rock chips to hit 3 GHz.
That's 67 percent more oomph just from clock speed alone, and it gets
Sparc chips humming at the same clock speeds as Opteron and Xeon
processors. But this theoretical clock speed improvement is mitigated
by the fact that Sun appears to be moving from 144 cores with the E25K
down to 128 cores with the top-end Rock machines. When you wash it all
out, it should be a 1.5X performance increase. How, add in the effect
of simultaneous multithreading and the "scout" threads that the Rock
will have. SMT should be a 40 percent boost right there, which puts you
at 2.1X. The scout threads are not traditional instruction streams, but
a means of running instruction streams way ahead to make sure local
cache memories have the data they might need as the real instruction
streams progress through the CPU cores. This is a very sophisticated
kind of prefetching that instead of predicting what data is needed
actually runs ahead real fast in the instruction stream and gets the
data. (Maybe this is unsophisticated
and therefore very smart.) Sun has been vague about the scout threads
and their effect on performance, but it is safe to assume that it is
substantial.
Moving to fully buffered DIMM main memory, and having a lot of it--128
DIMMs on the two-chip Rock machines and 512 DIMMs on the eight-Rock
versions, reportedly--is also going to significantly boost performance,
too, for the Rock chips. And if Sun moves its main memory controller as
well as cache controllers and tables onto the Rock, chip, too, this
will provide a big performance boost.
Here's what I want to know: What does "RK" really stand for? Real Killa? Rice Krispies? Radial Keratotomy? R.K. Narayan?
Read the original article: http://www.itjungle.com/tug/tug041207-story03.html
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