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Old 05-16-2007, 02:14 PM   #1 (permalink)
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Default How does over clocking with DDR2 work?

I'm a little confused here. This will be my first time ever using or working with DDR2 RAM, so I don't have much experience here.

With say, DDR400 RAM, it has a real clock of 200MHz with an effective clock of 400MHz. I'm pretty sure it gets the real clock of 200MHz from the FSB, as whenever you increase the FSB the RAM also increases.

So now take my DDR2 800 RAM. It has a real clock of 400MHz and an effective clock of 800MHz. How does it get that? I still have a FSB of 200.

Does it have something to do with a CPU/DRAM ratio? Does it not run at 1:1?

I'd like to start over clocking my new rig but I'm a little confused about this.

Thanks.
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Old 05-17-2007, 02:15 AM   #2 (permalink)
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Default Re: How does over clocking with DDR2 work?

Anyone?
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Old 05-17-2007, 07:34 AM   #3 (permalink)
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Default Re: How does over clocking with DDR2 work?

400MHz is default for the DDR2-800. You can set it to 1:1 ratio though, so they can match.
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Old 05-17-2007, 11:55 AM   #4 (permalink)
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Default Re: How does over clocking with DDR2 work?

But would that make it run at it's full speed or at the speed of the FSB?
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Old 05-17-2007, 12:27 PM   #5 (permalink)
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Default Re: How does over clocking with DDR2 work?

It won't make the ram run at the full 400MHz, if it's set to a 1:1 ratio. It will run the same speed as the FSB, which is 200MHz. If you want to run it at 400MHz, then you should overclock the FSB to 400MHz. But do it slowly. Don't go straight into 400MHz. Also if you set the ram to 400MHz and the FSB is still at 200MHz, whats the use of having the ram run at full speed, when the FSB is slower than the ram.
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Old 05-17-2007, 03:12 PM   #6 (permalink)
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Default Re: How does over clocking with DDR2 work?

Hmm..

So even if the RAM runs at 400MHz, it's really only taking advantage of 200Mhz since that's what the FSB is?
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Old 05-17-2007, 03:21 PM   #7 (permalink)
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Default Re: How does over clocking with DDR2 work?

Yes, because the FSB is the channel, through which your whole system communicates. My ram is running at 412, so my FSB is running 412.
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Old 05-17-2007, 07:08 PM   #8 (permalink)
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Default Re: How does over clocking with DDR2 work?

and really, you're ram doesnt need to be exactly on a 1:1 ratio with an amd chip. it doesnt really make that big of a difference. howerver i do notice a significant improvement when i run super pi with my ram oc'd high (i.e. running at 450+ mhz...way above my fsb)versus running it at stock (less than 400mhz...its an amd thing with integers and cpu multis). i chalk this up to amd's on-die memory controller. but technically, i dont know why it happens. i guess i need to do some research, because i just thought of something i dont really understand...doh. maybe it is because of the on-die controller. hrrrmmm. like, currently my ht link (LDT) is running at 840. this is with bus speed of 280x9.5 with a ht multi of 3 (3x 280 = 840). my ram is running at 442 mhz, and unless i clock it to 840mhz (hahaha) i still have headroom between my cpu and ram speeds. which means that if i clock my ram to 550mhz, i am still okay as well as long as that ht link stays above 550 i will be getting full usage of both components.
i think i just figured it out. ok i knew it was in there (my head) somewhere.
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Old 05-17-2007, 07:21 PM   #9 (permalink)
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Default Re: How does over clocking with DDR2 work?

DDR2 Ram with a chip that has a FSB of 200 can be run on a 1:2 ratio which is faster than a standard 1:1.
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Old 05-19-2007, 10:46 AM   #10 (permalink)
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Default Re: How does over clocking with DDR2 work?

hopefully i can gte my system at 1:1 cant see it happening though
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