Author: Aaron Gordon
Date: 14:02:22 03/18/03
Go up one level in this thread
On March 18, 2003 at 16:41:03, Robert Hyatt wrote: >On March 18, 2003 at 15:42:56, Aaron Gordon wrote: > >>On March 18, 2003 at 10:12:56, Robert Hyatt wrote: >> >>>On March 18, 2003 at 00:24:01, Aaron Gordon wrote: >>> >>>>On March 18, 2003 at 00:01:44, Robert Hyatt wrote: >>>> >>>>>On March 17, 2003 at 22:59:30, Aaron Gordon wrote: >>>>> >>>>>>On March 17, 2003 at 18:47:27, Eugene Nalimov wrote: >>>>>> >>>>>>>I just run the experiment. I used 2 otherwise identical 64-bit systems, one with >>>>>>>3Mb of L3 cache, other with 1.5Mb. Machine with bigger cache run Crafty's >>>>>>>"bench" comman 12% faster (1 CPU). >>>>>>> >>>>>>>That means that >>>>>>>(1) Crafty's working set don't fit into 1.5Mb, >>>>>>>(2) For systems with cache 1.5Mb or less (i.e. for almost all x86 systems) for >>>>>>>Crafty memory speed matter. >>>>>>> >>>>>>>Thanks, >>>>>>>Eugene >>>>>> >>>>>>Those types of systems aren't what people normally use. Most people here have a >>>>>>Pentium 3, Athlon, Pentium 4, etc. Here is something I found with Crafty. >>>>>> >>>>>>Using the Nforce2 chipset I'm able to run the ram at speeds from 50% up to 200% >>>>>>(100% being synchronous) of the fsb speed. I tested 200MHz FSB (400DDR) with >>>>>>200MHz memory (400DDR) and 200fsb with 100MHz memory (200DDR). >>>>>>The difference between ~1.6gb/s memory and ~3.2gb/s memory with craftys 'bench' >>>>>>command was 0.14%. Yes, about one seventh of one percent. >>>>> >>>>>That might well suggest _another_ bottleneck in that particular machine.... >>>> >>>>Another bottleneck? What was the original one? >>> >>> >>>The original one was assumed to be bus speed. That's where I entered the >>>discussion. But bus speed is not the _only_ issue that can cause problems >>>here. >>> >>>Lack of interleaving is another. >> >>All modern single cpu computers have 4 way/4 bank memory interleaving. Even my >>old dual Celeron box has 4 bank/4 way interleaving... > > >Most do _not_ support interleaving. I'm _specifically_ talking about four banks >to do >four consecutive 8-byte reads at once, then you want for the initial 120ns >delay, and grab >the first 8 bytes, followed by the remaining 24 bytes on the next 3 bus cycles. >Repeat to >fill a cache line. > >I am not aware of _any_ single-cpu machines with interleaving. You have to have >a machine >with 4 banks, with 4 SIMMS/DIMMS/etc as well. > >Give me a model number for your celeron and I'll look. But Unless you have four >separate >DIMMS in it, it ain't doing 4-way interleaving. The motherboard is an Abit BP6. There's also 4-way interleaving on the Abit KT7, KT7a, BH6, Be6, Be6-2, BX6, BX6-2, etc. Tons and tons of boards support 2 & 4 way. Also if I recall correctly it treats 1 dimm as "2" banks. Back in the day when enabling 4-way interleave with two Kingmax PC150 dimms (256mb per) I saw at least a 20% fps increase in Quake3. I still have the KT7a if you want me to run any tests.
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