Author: Vincent Diepeveen
Date: 12:45:25 01/29/05
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On January 29, 2005 at 14:52:58, Dan Andersson wrote: > Yes. it's true we don't know everything about the architecture right now. > But it is actually not a totally bad idea to have caching as part of the API. >It would be wonderful for a program written using declarative concurrency for >example. >MvH Dan Andersson I didn't read all advertising slogans from Cell processor yet. What i just don't understand is how they can clock it high AND produce it cheap. I'm not really an idiot there. I do understand that if you want a 1 cycle L1 cache with 2 ports AND this cache to be say 512KB or something, that even in 0.065 it won't clock to 4.6Ghz. In fact in todays technology when you want to produce a processor like that, and now i assume something where one produces tens of millions from, such a processor would cost even if it is 2Ghz clocked with 8 execution cores having 512KB, at least $4000, as the core will be at least 8 * 50 = 400mm^2. Even a layman can do that math. That is in fact bigger than todays itanium2 which sells for $4300 if you can get it for that price that is. You have to buy a 1000 of them to get them for that price. We're talking practical about $70000 for a quad itanium2 at 1.5Ghz. Now IBM plans 4.6Ghz. That's a tad 'ambitious' for memory that's faster than any cache existing. The only reason why intel can earn so much money is because their L1 cache at the P4 is just 8KB or 16KB and it's nowadays at 3.8Ghz having a 4 cycle latency and just 1 port. Now compare this with this cache which must be hundreds of KB's and is 1 cycle and has 2 ports. If you reduce that 'fast memory' that each of the 8 help cores have, to say 128KB, then what software are you going to run at it? Because L2 cache lookups will not be possible as there is no L2 cache in this plan. For sure DIEP or Shredder or any future chessprogram will be having a problem as they don't fit very well in that 128KB. So let's for now assume Cell runs at 1Ghz. Even then it will be an impressive processor. But what will be its price? Also suppose it produces in 2007. How does a 1Ghz processor compare to a dual core 3.6Ghz opteron then? Vincent
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