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Subject: Re: Full circle

Author: Dezhi Zhao

Date: 10:44:03 08/29/03

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On August 29, 2003 at 12:36:28, Vincent Diepeveen wrote:

>On August 29, 2003 at 08:49:09, Dezhi Zhao wrote:
>
>>On August 28, 2003 at 11:45:35, Robert Hyatt wrote:
>>
>>>I'm not talking about write-through.  I am talking about write-back.  Once
>>>you modify a line of cache, that line of cache _is_ going to be written back
>>>to memory.  When is hard to predict, but before it is replaced by another cache
>>>line, it _will_ be written back.  So you write one byte to cache on a PIV, you
>>>are going to dump 128 bytes back to memory at some point.  With only 4096 lines
>>>of cache, it won't be long before that happens...  And there is no way to
>>>prevent it.
>>>
>>
>>Are the cache line sizes of L1 and L2 are different for P4? I was always
>>thinking of a L1 load or store is 64 bytes.
>
>yes they are way smaller than 64 bytes. Only to the slow memory it is 128 bytes
>at the P4 and 64 bytes at the K7. Opteron i don't know yet.
>
>You can look in the processor manuals how many bytes each L cache can get at a
>time. It's different for each processor seemingly.

I just checked. For L1 cache line size of P4, it is 64 bytes. I did not find the
L2 cache line size.


>
>A lot of criticism was there not too long ago, about the new transmeta chip
>which is getting some big size at a time. 128 bytes or something.
>
>Great for DSP but probably not so great for computerchess :)
>
>Best regards,
>Vincent



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