Maramba (T5240) Unplugged: A Look Under the Hood
By Josh Simons on Apr 10, 2008
Aside from being interesting machines for HPC, our latest systems are beautiful to behold. At least to an engineer, I suppose. We had a fun internal launch event (free ice cream!) on Sun's Burlington campus yesterday where we had a chance to look inside the boxes and ask questions of the hardware guys who designed these systems. Here is my annotated guide to the layout of a T5240 system.
A. Software engineers examining the Sun SPARC Enterprise T5420. Note the uniforms. Sometimes I think the hardware guys are better dressers than the software folks.
B. Front section of the machine. Disks, DVD, etc, go here.
C. Ten hot-swappable fans with room for two more. The system will compensate for a bad fan and continue to run. The system also automatically adjusts the fan speeds to control the amount of cooling needed, depending on demand. For example, when the mezzanine (K) is in place, more cooling is needed. If it isn't, why spend the energy spinning the fans faster than you need?
D. This is a plexiglass air plenum which is hard to see in the photo because it is clear though the top part near the fans does have some white-background diagrams on it. The plenum sits at an angle near the top of the photo and then runs horizontally over the memory DIMMs (F). It captures the air coming out of the fans and forces it past the DIMMS for efficient cooling. The plenum is removed when installing the mezzanine.
E. These are the two heat sinks covering the two UltraSPARC T2plus processors. The two procs are linked with four point-to-point coherency links which are also buried under that area of the board.
F. The memory DIMMs. On the motherboard you can see there are eight DIMM slots per socket for a maximum of 64 GB of memory with current FBDIMMs. But see (K) if 64 GB isn't enough memory for you.
G. There are four connectors shown here with the rightmost connector filled with an air controller as the others would be in an operating system. The mezzanine assembly (K) mates to the motherboard here.
H. PCIe bridge chips are here in this area, supporting external IO connectivity.
I. This is the heat sink for Neptune, Sun's multithreaded 10 GbE technology. It supports two 10 GbE links or some number of slower links and has a large number of DMA engines to offer a good impedance match with our multithreaded processors. On the last generation T2 processors, the Neptune technology was integrated onto the T2 silicon. In T2plus, we moved the 10 GbE off-chip to make room for the coherency logic that allows us to create a coherent 128-thread system with two sockets. As a systems company, we can make tradeoffs like this at will.
J. This is where the service processor for the system is located, included associated SDRAM memory. The software guys got all tingly when they saw where all their ILOM code actually runs. ILOM is Sun's unified service processor that provides lights out management (LOM.)
K. And, finally, the mezzanine assembly. This plugs into the four sockets described above (G) and allows the T5240 to be expanded to 128 GB...all in a two rack-unit enclosure. The density is incredible.