Author: Vincent Diepeveen
Date: 09:08:24 09/28/00
Go up one level in this thread
On September 28, 2000 at 01:17:48, Dan Newman wrote: >On September 27, 2000 at 19:47:09, Vincent Diepeveen wrote: > >>On September 27, 2000 at 19:29:53, Eugene Nalimov wrote: >> >>>RDRAM-to-CPU latency is not 4 times faster when you are randomly access memory. >>>Actually, it easily can be *higher* than for SDRAM-100. >>> >>>RDRAM shines when you are moving a lot of data around using sequental memory >>>access -- i.e. memcpy() kilobytes of memory. I doubt you often do that in Diep. >> >>I am quoting RDRAM-to-CPU latency from the tables as shown, >>which is higher as SDRAM, >>HOWEVER RDRAM runs at faster speeds as SDRAM ever will run >>(ddr ram is really the maximum one will ever be able to get out >>of SDRAM technique, after that we'll only see similar developments as >>RDRAM), so the number of clocks delay for a random lookup should be >>what i wrote in the example, unless the person making the article >>didn't very accurate make the article. >> >>So where the latency of fast SDRAM is 10T, for RDRAM it's 15T, >>yet RDRAM runs at 1.25ns, and SDRAM 133Mhz at 7.5ns, so that's where >>the big win for RDRAM is. >> >>I multiplied the 2 with each other and came down to my relative >>calculations that SDRAM getting a single memory line is 4 times slower >>as RDRAM. >> >>There are very CONFUSING pieces of information with regard to >>RDRAM versus SDRAM, that's the one thing i'm 100% sure of, if anyone >>reading this has RDRAM to his avail i'll be happy to deliver a free >>copy of diep to him/her if this person is the first to test the speed >>of diep at RDRAM. >> >>>For technical deyails you can take a look at >>> http://www.realworldtech.com/page.cfm?ArticleID=RWT110799000000 >>> http://www.realworldtech.com/page.cfm?ArticleID=RWT112299000000 >>> http://www6.tomshardware.com/mainboard/00q1/000315/index.html >> >>Yeah i read those too, not exactly what i want to know. Most >>interesting for chessprograms are getting at a random place in >>memory a byte or 32 to 128 at most. >> >>>Eugene >>>On September 27, 2000 at 18:46:57, Vincent Diepeveen wrote: >>>>On September 27, 2000 at 16:22:52, Dan Andersson wrote: >>>>>Do you have any benchmarks supporting your view? I'm just asking as I don't have >>>>>any. A benchmark simulating random accesses of small fragments of memory should >>>>>do it. The architectural design choices taken when designing RDRAM seems to go >>>>>against what you say. Namely, its time expensive to select a new memory location >>>>>to read from. A chess program would need to read a fair amount of data from >>>>>memory to mortgage that. But then again every programs mileage may vary. RDRAM >>>>>is hot coupled to streaming data and SIMD instructions. >>>>> >>>>>Regards Dan Andersson >>>> >>>>when i took my draughtsprogram from EDO ram to SDRAM it was hell faster >>>>suddenly. Now i heart RDRAM is slow. So i looked up latency. >>>> >>>>Latency is 4 times faster, not because the latency itself is faster, but >>>>because latency times speed at which the RAM runs is so little compared >>>>to SDRAM 133Mhz. >>>> >>>>So practically there is simply no discussion. This runs a lot faster. >>>> >>>>Yet when we talk about *how much does it speed me up*, then we really >>>>get to an interesting question as i don't know! >>>> >>>>i didn't test it yet at all, i was just amazed that this new technology >>>>is cracked down to the bottom in all kind of articles where it's obviously >>>>a lot faster for me as *any* sdram, whether it's DDR or not! >>>> >>>>Yet not everything fits in 256kb L2 cache for sure, so it's not only >>>>the hashtable lookups that are profitting bigtime from it, also the many >>>>evaluation tables and all kind of tables used to lookup things are profitting >>>>from it. >>>> >>>>The huge profit is basically caused by the huge slowness of a lookup >>>>at the current SDRAM. >>>> >>>>In my dual PIII800 slot1 there is no 133Mhz SDRAM. My supermicro motherbord >>>>doesn't even support it! >>>> >>>>i have 100Mhz SDRAM. >>>> >>>>That's another 33% slower *at least* as 133Mhz. >>>> >>>>So a single lookup in memory is in its most realistic case: >>>> 10ns x 11T = 110 clocks. >>>> >>>>You can do a lot in 110 clocks! >>>> >>>>If that gets suddenly down to less as 20 clocks, then >>>>it's clear that this rocks bigtime. >>>> >>>>considering the huge number of tables in my program which all together >>>>eat hundreds of kilobytes of RAM, i'm estimating that speedup *might* >>>>be like 20% or so in the middlegame for DIEP. >>>> >>>>However programs that are very fast and are basically wasting their system >>>>time at hashtables might profit even more. I wouldn't be amazed by a 2 fold >>>>speedup for certain programs. >>>> >>>>That's what EDO ram to SDRAM did for my draughtsprogram at least... > >I actually tried an RDRAM machine recently. I ran my chess program benchmark >(WAC at 1s/posn) on a P3/933 + PC800 and got 1060 knps. I have a P3/933 with >SDRAM at home. On that system I get 1083 knps. > >So, at least with my program, SDRAM is slightly better. I suspect that SDRAM >will actually be a whole lot better if your program is at all memory speed >bound. Mine isn't apparently: when I set the memory to run at 100 MHz instead >of 133 MHz (which I can do independent of the FSB speed with the motherboard >I'm using) I get 1066 knps--which is still faster than the RDRAM result... >-Dan. I'm amazed! What SDRAM133 do you have at home, 2-2-2, 2-3-3 or 3-3-3? the difference between 2-2-2 (which is the fastest) and 3-3-3 should be a bit less as 10% for latency. What chipset did the machine have where you tested the rdram at and how many banks of RIMMS did it have? Thanks in advance, Vincent
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