Author: Vincent Diepeveen
Date: 15:46:57 09/27/00
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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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