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Subject: Re: hardware question (SDRAM or DDRAM?)

Author: Jeremiah Penery

Date: 10:55:47 12/04/02

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On December 04, 2002 at 13:32:01, Vincent Diepeveen wrote:

>On December 04, 2002 at 11:42:17, Matt Taylor wrote:
>
>>On December 04, 2002 at 10:43:59, Vincent Diepeveen wrote:
>>
>>>On December 04, 2002 at 10:21:08, James T. Walker wrote:
>>>
>>>>On December 04, 2002 at 08:00:35, martin fierz wrote:
>>>>
>>>>>hi,
>>>>>
>>>>>i'm on the lookout for a new PC for endgame database computations. i'll probably
>>>>>be buying a lot of ram, 2-3GB. i see that there is a big price difference
>>>>>between DDRAM and SDRAM. IIRC the main difference is that you get a larger
>>>>>bandwidth, but about the same latency with DDR - so i suppose i'm better off
>>>>>buying SDRAM for my application. any opinions of the experts?
>>>>>
>>>>>thanks in advance
>>>>>  martin
>>>>
>>>>For what it's worth:  I purchased one stick (256M) of DDR ram to compare to my
>>>>cheap SDRAM.  I found no noticable difference in chess performance (just price).
>>>> I did not do any extensive testing.  I simply compared Fritz marks.  I suspect
>>>>that in the future most motherboards will not accept the SDRAM.
>>>>Jim
>>>
>>>I see a big difference. 64 versus 32 bytes cache lines matters
>>>a lot for DIEP and all software that doesn't fit within L1 cache.
>>>
>>>Best regards,
>>>Vincent
>>
>>Cache line size is a part of the CPU, not the ram. There are a number of
>>transitional products, both P4 and Athlon, that accept both SDRAM and DDR SDRAM.
>>(However, I have never heard of anyone happy with these products.)
>
>the P4 ended up being a lot faster for DIEP when i tested a p4 with ddr ram
>isntead of RDRAM.
>
>P4 with ddr ram (northwood) is like 1.5 : 1 for a K7
>used to be 1.7 : 1 to a k7 with rdram.
>
>So 1.7 Ghz P4 rdram == 1.0Ghz K7 for DIEP
>   2.4 Ghz P4 ddr   == 1.6Ghz K7 for DIEP (both ddr).
>
>DDR is a big step forward!!
>
>i don't know where the processor gets 64 bytes instead of 32 bytes in
>the design. I just know it gets 64 bytes, versus SDRAM 32.

Hash probes in a chess program depend on latency, not bandwidth.  RDRAM sucks
for latency, where it is at least double that of SD/DDRAM.
For the tablebase creation, I would expect this to depend much more on streaming
bandwidth - there, RDRAM will win.



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