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How do you count cores? Or should you?

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krisi
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re: How do you count cores? Or should you?
krisi   3/12/2012 6:28:02 PM
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I don't really care how many cores are inside my laptop...but I would like to see some metric when buying a new one so I can make an informed decision...ideally it would benchmark some activity I routinely do...Kris

nicu_p
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re: How do you count cores? Or should you?
nicu_p   3/12/2012 4:24:21 PM
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Intel HT *does not* provide a performance increases comparable to adding another core. 10-15% is the maximum one can hope for, depending on the tasks at hand, and for some type of applications it is better to just disable it (typically when one needs some degree of predictability on the threads that are executing).

przemek0
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re: How do you count cores? Or should you?
przemek0   3/7/2012 9:25:31 PM
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As if this wasn't complicated enough, there are tricks like Intel's hyperthreading. Essentially, you never have complete duplication--there is always a shared resource that tends to be the bottleneck. For an ideal two core system it'll be the main memory interface where all the cores fight for access---but it could also be the memory controller, or one or more cache levels. In the case of hyperthreading, the only duplicated resource is essentially the processor context (registers, flags, PC, interrupt state, etc). The reason why HT usually but not always gives a performance boost is that it masks the main memory access latency. The trip through the virtual-physical address translation, caches and memory controller takes dozens of CPU cycles; if there's another thread with data already loaded in the registers, it can be run while the original thread waits for its data being loaded. In an ideal case, both threads ping-pong masking each other's memory latency.

chanj0
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re: How do you count cores? Or should you?
chanj0   3/7/2012 12:03:38 AM
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Benchmarking is the best way to measure performance even though most benchmark tests are difficult to understand. Not to mention, benchmark tests are often disconnected to the "real world" experience. To my experience, the best way is to understand what you need a computer for and buy the one that fit your usages for next 3-5 years. Believe me, often time, only 25% of each core of a quad-core processor is utilized.

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