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FSB and RAM ????

  • RAM
  • CPUs
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  • Overclocking
Last response: in Overclocking
August 3, 2008 6:35:53 PM

Ok I have two 1 GB sticks of pc6400 (800 MHz) RAM, I have an e7200 CPU over clocked to a 1333 FSB. Now when I was over clocking in my BIOS I have 3 options and they were "linked", "unlinked", or "Sync". I was instructed to choose Sync for the best performance results so I did. I noticed that choosing sync with a 1333 fsb made my RAM run at 667 MHz, I do not fully understand why its better to run at 667 vs say 800. I know that intels FSB is quad pumped which means 1333 is actually four 333MHz "pipelines" to the motherboard. I also heard that RAM is dual pumped so 800 MHz ram is actually two 400 MHz "pipelines" to the motherboard. does Sync dial down my pc6400 800 MHz RAM to 667 because then the RAM two pipelines to the motherboard are 333 Mhz each which is the same size pipelines comeing in/out of the CPUs FSB? If that is the case then why is pc6400 RAM so popular and now even 1066MHz RAM is starting to catch fire when I think most people only have 1066/1333 FSB CPUs. 1600 FSB is starting to be more popular in highend chips but still PC6400 800 MHz RAM is the max you ever really need, and 1066 MHz and DDR3 speeds seem pointless for performance gains unless there is something Im still missing here.

Another thing I am wondering if RAM is only dual pumped but CPUs FSB is Quad, is that the purpose for dual channel RAM so one channel dual pumps into two of the FSB pipelines and the other channel into the other FSB two pipelines?

Please feed my thirst for understanding and wisdom!

More about : fsb ram

August 3, 2008 7:01:03 PM

pc6400 800mhz ram can support an FSB of 1600mhz...

i don't exactly know how to explain this with the correct terminology, so I won't even try, but setting your ram to 667mhz syncs it with your cpu [fsb of 1333] to have a 1 to 1 ratio... here i have a link
August 3, 2008 7:16:05 PM

eh sry that link really didn't help me but thx at least for trying
Related resources
August 3, 2008 7:54:36 PM

eklipz330 said:
pc6400 800mhz ram can support an FSB of 1600mhz...

i don't exactly know how to explain this with the correct terminology, so I won't even try, but setting your ram to 667mhz syncs it with your cpu [fsb of 1333] to have a 1 to 1 ratio... here i have a link

Yeah, if you run RAM at 1:1 with FSB, you would have a 400mhz base clock which equals DDR2 800 and 1600mhz FSB. I'm running my Q6600 like that right now, 400mhz x 8 (3.2ghz), 1600mhz FSB DDR2 800.
August 3, 2008 8:04:17 PM

ok well let me ask you this... Im running 1:1 on 1333 FSB which equal 667 would there be a performance gain if I ran 5:4 giveing me 833 on my RAM?
August 3, 2008 10:36:53 PM

^ there would be theoretically no benefit of running your system in this configuration as the RAM would just be sitting around doing nothing for those extra MHz....1066MHz DDR2 is 1: purely hype
2:for stupid people who think they have to have RAM that matches their CPU's QDR (in your case 1333, but you don't obviously, as RAM is dual pumped....)
and 3: some people buy it, underclock it to 800MHz or whatever, and tighten the timings HEAPS to hopefully make it faster than stock 800MHz....btw 1066 is purely factory overclocked 800MHz with relaxed timings.

and also for enthusiasts with like liquid nitrogen and 2000MHz+ QDR's.... theres a board that can overclock to over 700MHz FSB = 2.8GHz QDR!! that means 1400MHz RAM, lol...

so, to answer your question, no you would not get any increased performance in a 5:4 as opposed to 1:1... i reccommend lowering your timings a bit if you're running at 667....use CPUz's RAM timing tables to figure out...should be at least 4-4-4-12 depending on the quality of your RAM, if not lower.
August 3, 2008 10:39:01 PM

i hope that cleared things up :p 
a c 137 à CPUs
a c 136 V Motherboard
a b K Overclocking
August 4, 2008 12:47:16 AM

Because its a higher number, so people (well, more like noobs) think its good/better. The same thing happens when people buy the 1GB model of the 8600GT because 1GB is better then only 512MBs on the 8800GT. Just because something is "more" doesn't mean its better.

Do me/you/us a favor. Test it for yourself. You seem to understand how/what your doing, try it and see. Fire up your favorite game and get a frame rate with FRAPS. Rip a DVD with DVDshrink and note how long it takes. Unzip a large zip file. Now, change the ratio so that your running at 800MHz instead of 667. Is there a large difference? You will probably see better times with 800 over 667, but it should be a small PERCENTAGE. This will be mostly due to burst transfer rates.

Back when DDR2 first came out, I told people they should get 667MHz ram instead of the (then) more expensive DDR2-800. Seeing as there is now little difference, you should just get the DDR2-800. Doomturkey has it right. Set your FSB to 400, lock the ram, and set the multiplier as high as you can while staying stable. With Intel CPUs, it doesn't get easier then that.
August 4, 2008 12:51:56 AM

Indeed! Thanks for that insight. So how dangerous is it to take the timing on RAM to say 3-4-4-9 when the original factory timing are 4-4-4-12? Also is the reason dual channel exists because RAM is dual pumped but when you have 2 stick of RAM dual pumping on two different channels it makes it like the RAM is quad pumping into the CPUs Quad pumped FSB?
August 4, 2008 1:00:05 AM

This machine is not for gaming and I bought a cheeze ball MB so cheezeball I can't even look at the multipler, not the best overclocker but all this is preparing me for my next "real" OC on a good motherboard, nice after market cooler,and hopefully a nice CPU...this is actually for my parents mostly but I want to see how fast I could make this budget machine go and get some experience.
August 4, 2008 1:13:00 AM

the dual channel RAM does not increase the effective speed of the RAM, simply bandwidth.... i would say lower the timings to 3-4-4-12, then 3-3-4-12 etc until it fails memtest.
August 4, 2008 10:49:11 AM

btw i bet i got a worse mobo than urs :(  cant change the multiplier on my CPU ffs....