Niagara Multicore versus Multi-Threaded

In my previous experience with Sun systems, I've noticed that the Intel Xeons (shipped with the old v60z) were appearing as multi-CPU. Solaris would show one physical CPU demonstrated as two. In reality, each of those "virtual CPUs" are threads running on a single CPU. This isn't multicore. As I now know, the Xeon CPU was running with two threads.

Now that I'm playing with the Niagara systems, I'm really seeing what it means to be multi-core. On powerup, we received 8-Core Niagara boxes. Solaris "mpstat" however showed a whopping 32 processors!!

According to Marc Tremblay.. "Each of Niagara's eight cores can process four software threads, or tasks, simultaneously - all while using no more energy than the average lightbulb (as little as 10 percent of what other processors use)."

To a software and deployment guy like me, this is pretty wild. Now we can push our Messaging Server and Calendar Server to a smaller footprint in the rack. Using Solaris Zones we can create multiple Calendar and Message Store instances which avoid the negative problems associated with Sleepcat databases. Look for a paper to be published on this configuration later. :)

Marc Tremblay's Explaination of Multicore Strategy

Comments:

yeah, the Intel HyperThreading is a neat trick - but nowhere near the league of multicore. basically it has multiple instruction streams going down the same pipeline. it keeps two sets of registers, each one containing the state of one thread. when the currently running thread blocks (ex: memory stall), then the CPU can switch to the other set of registers. so it's a \*really\* fast context-switch (since it doesn't have to do any register swapping), but still a context-switch none the less.

Posted by stevel on October 18, 2005 at 09:29 AM PDT #

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