Author: Vincent Diepeveen
Date: 15:27:11 12/04/02
Go up one level in this thread
On December 04, 2002 at 17:16:15, Matt Taylor wrote: >On December 04, 2002 at 14:28:23, Vincent Diepeveen wrote: > >>On December 04, 2002 at 13:55:47, Jeremiah Penery wrote: >> >>>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. >> >>Not at all. Practical bandwidth from DDR ram is better. >> >>But besides from that in my own generator i can put an entire >>6 men bitmap in RAM (one side to move win or loss in N moves to >>conversion). >> >>That means that latency there is the only important thing. >>Harddisk speed is simply irrelevant compared to RAM latency. >> >>You can get next buffer from positions sequential from harddisk >>which is about with 160MB/s that's like 1 billion positions. >> >>getting the like 20 equivalent moves from that from RAM is the >>major problem. Of course skipping already the ones that are >>already known to be either winning or losing (depending upon >>what pass you are at). >> >>All those lookups are in RAM therefore. harddisk speed is >>irrelevant. Is anyway irrelevant knowing how much ram nowadays >>systems have. >> >>A single 6 men with pawns buffer is like 18G entries. >> >>To give example from my own simple generator (i do not use the >>extra optimizations nalimov uses, because it slows down the >>indexing function too much as i want to generate all 6 men within a >>year instead of many years; cpu speed is the limiting factor): >> >>159 kbnkbp 00240041 18141551280 >> >>So that's for kbn kbp in my generator 18.1G entries. >> >>So looping sequential through the positions in small buffers, >>you can easily see that i can do random lookups to memory easily >>as this is just a bitmap of: 2267693910 bytes. >> >>That's very luckily smaller than 3 GB because windows doesn't >>allow more memory space than 3 GB if i am correct for my K7 computer >>and x86 in general. >> >>So a U160 SCSI disk and a machine that's just generating can generate >>all 6 men within a year. >> >>Of course i do not save the mate in 'n' positions. So when combining >>the bitmaps i just keep left with the 'win/loss bitmaps and create >>win/draw/loss from it instead of mate in n or loss in n, which nalimov >>saves. >> >>Then i compress it all. >> >>Uncompressed i have : >> >>In total 510 egtbs using 2631231208124 entries >> >>That's for 1 side to move. For both sides to move, just double it. >> >>So say 5.22 Tera entry. >> >>that's uncompressed 5.22 / 5 positions a byte = 1.044 Terabyte to >>store. >> >>That compressed will go to i suppose around 150GB. >> >>Perhaps i can get it smaller. Still toying with Andrew Kadatch superb >>compression there. >> >>All 5 men fit at 1 CDrom. > >Theoretical bandwidth on pc2100 DDR is 2.1 GB/sec. Theoretical bandwidth on >pc2700 DDR is 2.7 GB/sec. Theoretical bandwidth on pc800 RDRAM is 3.2 GB/sec. I >used to have a P4 1.5 GHz with 768 MB pc800 RDRAM. The system had 2.8 GB/sec >empirical bandwidth, which is higher than pc2700 DDR SDRAM theoretical >bandwidth. tested bandwidth the DDR scored way higher on different sites, but as i explained in other posting i don't want get into that forever yes/no discussion. It is a discussion which never stops. For latency the thing are very clear though. when talking about normal PC2100 DDR ram versus way more expensive normal PC800 RDRAM: 100Mhz at 15 T for RDRAM (128 bytes) 133Mhz at 10 T for DDRAM (64 bytes) So the latency of DDR ram is exactly 2.0 times faster (15/10) * (133/100) Obviously P4s with DDR ram perform 2 times better for EGTB generation which is looking up a random byte from a 2.2GB memory pool than RDRAM will do. No discussions here. Case is very clear.
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