Author: Robert Hyatt
Date: 07:57:59 08/25/02
Go up one level in this thread
On August 25, 2002 at 10:09:33, Dan Andersson wrote: >> >>The multiprocessor versions of the Hammer will be what most guess it is. >>It is more like a NUMA system. Getting data from local memory is very >>fast (faster than RAM is now), but on the other hand getting data from >>other nodes is a lot slower. >> >Not a lot slower actually. And factoring in the faster memory speeds you will >not be hit by it at all. Since the memory controllers and the communication >ports are connected to the CPU core by the same type of bus. And the latency >will be lower the faster the CPU goes. Down to an asymtotic constant limit. So >you need *no* complete redesign to run Crafty fast. No redesing at all, >actually. But to get the absolute maximum you need to factor in the hardware. > >MvH Dan Andersson If you look at my response to Vincent, there are a few issues that need addressing because NUMA introduces a much higher memory latency for processors that are farther away from the actual memory word needed. This has to be addressed to produce reasonable speedups. There are plenty of NUMA machines around today, notably from SGI, which can be used to understand these issues... BTW memory latency has been constant for 20+ years now. But as the speed of the processors goes up, memory becomes relatively slower. So long as we use capacitors for bit storage, this is going to continue to remain a big issue.
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