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Subject: Re: Some thoughts for those who are considering to buy a Dual processor PC

Author: Robert Hyatt

Date: 06:36:54 03/27/01

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On March 27, 2001 at 08:52:15, Andrew Dados wrote:

>On March 27, 2001 at 08:17:43, Vincent Diepeveen wrote:
>
>>On March 26, 2001 at 22:44:53, Robert Hyatt wrote:
>>
>>>On March 26, 2001 at 20:54:48, Dan Andersson wrote:
>>>
>>>>I have to agree that multibanked memory and lage cashe size are very beneficial.
>>>>Those factors could very well explain the superlinearity.
>>>>
>>>>Regards Dan Andersson
>>>
>>>
>>>I don't think the 4-way interleaving helps.  That _barely_ lets the machine
>>>hold its own, memory-wise, because there are 4x as many cpus fighting over
>>>access to memory... making it nearly 4x faster just barely breaks even.  The
>>>larger L2 cache may well make a difference, of course...
>>
>>You speak for Crafty. I speak for DIEP.
>>I'm doing 8 probes of at least 16 bytes an entry.
>>that's 128 bytes.
>
>My guess is big difference for SMP DIEP is running separate processes instead of
>threads. 8 probes is just icing on that cake.
>
>For what I know windows (unix too) will load each process to its own address
>space, so they will fight for L3 cashe.
>Or am I totally wrong here?
>
>-Andrew-
>

This is correct.  Threads share one address space so this isn't such a huge
problem...



>
>>
>>I also do that to get a possible evaluation out of hashtable as i store
>>evaluations in hashtable.
>>
>>So i do way more of those octo-probes as most progs try the hashtable...
>>
>>Further my whole program is made out of 'int'. So that means in short
>>that all kind of tables are 4 times bigger (in bytes) as they could
>>be. That means that when compared to some years ago i need quite some
>>accesses to main memory.
>>
>>Both the bigger L2 cache and the faster memory helps a lot then.
>>
>>Best Regards,
>>Vincent



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