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Old 04-06-2007, 03:59 PM   #1
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Default Ram speed vs FSB speed & avoiding a bottleneck

I'm a little bit confused about this. I know people talk that having ram faster than your FSB is pretty much a bottleneck correct? So i'm going to use the core2duo as a example with PC6400 ram. I just want to know if my math is correct to get the best performance vs clock ratio.

So you have a native FSB of 1066 and Ram @ 400MHz X 2 = 800MHz Do I base the speed off this figure?

But heres the question if intels FSB is quad pumped 1066/4 = 266Mhz is this the true speed? Like the PC6400 without multiplying it X2 would be 400Mhz. Figuring it like that the ram is 134Mhz faster than the true FSB.

So I guess my final question is running ram in anything but 1:1 ratio benificial? I just ask because to go over 3Ghz on my system I need to run in a 1:1 ratio. Also in benching my ram I've noticed the bandwith is higher with a lower clock in 1:1 rather than say a 4:5 ratio. With those figures I'm kind of thinking, say 1333/667 is faster than 1333/800 because the ram is bottlenecked by the FSB.
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Old 04-06-2007, 04:32 PM   #2
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Default Re: Ram speed vs FSB speed & avoiding a bottleneck

ummm, it depends on what latencies your RAM has to run at. Of course 5-5-5 @ 1000mhz isn't as fast a 4-4-4 @ 800. But if you can run 4-4-4 @ 1000, it will be a lot faster than the one at 800. It doesn't really matter what your FSB is. If you can run 4:5 with good latencies, you are set.
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Old 04-06-2007, 04:39 PM   #3
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Default Re: Ram speed vs FSB speed & avoiding a bottleneck

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Originally Posted by ownage
ummm, it depends on what latencies your RAM has to run at. Of course 5-5-5 @ 1000mhz isn't as fast a 4-4-4 @ 800. But if you can run 4-4-4 @ 1000, it will be a lot faster than the one at 800. It doesn't really matter what your FSB is. If you can run 4:5 with good latencies, you are set.
ram timings and latencies have always kind of confused my , i know that 5-5-5 at 1000 aint as good as 4-4-4- at 800 but it kind of grinds my brain luckily i dont game and am not too bothered about ram timings in my computers
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Old 04-06-2007, 04:53 PM   #4
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Default Re: Ram speed vs FSB speed & avoiding a bottleneck

Okay all I know about ram timings is basically they stand for how many clock cycles it takes to complete a loop correct? So that would make sense that a lower latencies would improve speed. Whats the best way to go about reducing them? I know mine is 5-5-5-15 by default. Sould I adjust them all at one time or try 4-5-5-15 then go 4-4-5-15 reducing one by one.

From research this is what i've found the numbers to mean.

tRcd=5 (Ras to Cas delay)
tRP=5 (Ras precharge)
CAS=5 (Column address strobe)
tRas=15 (cycle time) - (Row address stobe) I've read this number should be a bit higher than the CAS + tRCD +(2) depending on module. How can I find out what the what number for sure to add to my ram. By the default it looks like it would be CAS + tRCD +5 right.

How would I calculate a new ram timing pattern then?
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Old 04-06-2007, 06:32 PM   #5
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Default Re: Ram speed vs FSB speed & avoiding a bottleneck

The way i did it was to lower each timing by one then test using everest ultimate edition in windows, then stick with that timing and keep lowering it and testing it until my pc wouldnt boot. Eventually after a day of solid testing i managed to increase my ram scores by about 2000mb/s. Takes patience but worth the time.
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Old 04-07-2007, 02:02 AM   #6
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Default Re: Ram speed vs FSB speed & avoiding a bottleneck

or, just run super pi 1M and see which one yields the faster time
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Old 04-07-2007, 07:37 AM   #7
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Default Re: Ram speed vs FSB speed & avoiding a bottleneck

Thanks for the info I'll have to check out those. So basically running ram in 1:1 is just fine just keep the timings as low a possible then.
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Old 04-10-2007, 07:42 AM   #8
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Default Re: Ram speed vs FSB speed & avoiding a bottleneck

Quote:
Originally Posted by muz379
ram timings and latencies have always kind of confused my , i know that 5-5-5 at 1000 aint as good as 4-4-4- at 800 but it kind of grinds my brain luckily i dont game and am not too bothered about ram timings in my computers
OMG HE DOESNT GAME!

[Sirens go Off]

QUICK HOLY WATER HOLY WATER!@

lol :P
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Old 04-10-2007, 08:18 AM   #9
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Default Re: Ram speed vs FSB speed & avoiding a bottleneck

Quote:
Originally Posted by Xiggy
OMG HE DOESNT GAME!

[Sirens go Off]

QUICK HOLY WATER HOLY WATER!@

lol :P
i dont game and i have sd ram in one of my comps so yeah i aint too bothered as ling as i can turn it on log onto the internet type up some word docs i am happy , i am thinking of building a gaming machine later this year when i get a job and stuff thenn i will care about them but for now i am ok
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