Author: Eugene Nalimov
Date: 16:29:53 09/27/00
Go up one level in this thread
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. 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 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...
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