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Topic Title: DDR2 533 - DDR2 800 Need some info
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Created On: 02/09/2007 04:46 PM
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 02/09/2007 04:46 PM
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Stix
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I been having this argument about adding DDR2 800 to my wifes X2 3800+ and the mobo supports it. Yet the person I am arguing with states that it will not use the ram. Here is his thinking.

quote:

Originally posted by: Unknown No, no... no. Not at all. The FSB (or HTT as it's now called, I still say FSB) of the processor only operates at 200mhz, ie DDR2 400 speeds, and because the memory divider by default will be 1:1, that means you'll get one memory cycle per cpu cycle. Just because you put DDR2 667 in doesn't mean that anything changes. Most likely, the memory is going to continue operating at DDR2 400 speeds with a 1:1 divider.

In the off chance the Dell motherboard can raise the divider to something exotic like 3:2 or 2:1 and/or does it automatically, you will still have the base throughput of 200mhz to the processor. No true BANDWIDTH increase, but there are more memory cycles occurring per cpu cycle. However, this doesn't really offer a performance increase.

Higher memory is only really sought after for overclocking applications, because raising the FSB of the processor automatically raises the memory's bus as well, so you can take advantage of higher clocked memory.

If you're going to buy memory, get something with a lower CAS, at least 4 if not 3. This is much more important than the speed in mhz, currently.




quote:

Originally posted by: Unknown Those numbers are for machines with a higher FSB.

The HyperTransport bus for a 3800+ is 1000mhz, that is FSBxHT multi which happens to be 5.

In order to get the bigger benefit you would either have to A, change the Hypertransport multiplier or B change the FSB.

Anybody wanna bet those options aren't on an OEM Dell? Anybody have a lot of success overclocking a $400 Dell in the past 5 years? :Looks around for raised hands: I didn't think so.



WTF is he trying to say? He seems to be talking gibberish. I thought that if your Mobo supports the ram you would not even need to touch the Bios. And will get more bandwidth.
 02/09/2007 04:49 PM
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k2aka111
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my brain itches...I'm not the smartest person(or maybe thats it) but that sounds like...me talking when I joined this forum??

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Selling Asus M2N32-SLI deluxe & X2 4200+. PM me if interested
 02/09/2007 05:09 PM
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mckennma
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What does the spec sheet say. Will it use DDR2 533, 667 and 800? 800 would be faster and improve performance over 533.

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 02/09/2007 05:15 PM
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Stix
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quote:

Originally posted by: mckennma
What does the spec sheet say. Will it use DDR2 533, 667 and 800? 800 would be faster and improve performance over 533.




Yes it does support ddr2 800 but he says it still will not run at ddr2 800 even if it shows it in the bios. I am ready to rip his head off stating he is very misinformed.
 02/09/2007 05:22 PM
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mckennma
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quote:

Originally posted by: Stix
Yes it does support ddr2 800 but he says it still will not run at ddr2 800 even if it shows it in the bios. I am ready to rip his head off stating he is very misinformed.



CPU bus won't be faster but the RAM will have more bandwidth.

-------------------------
Tyan Thunder K8WE
Dual AMD 280 Opterons
8GB NUMA enabled DDR333 2.5-3-3-7 RAM
PCI-X SCSI RAID
http://69.14.190.80
 02/09/2007 06:56 PM
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zir_blazer
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He thinks that the Base Clock is the only thing that defines the Memory Modules Frequencies and forgetted about the fact than the Memory Controller runs asyncroneusly because it uses its own Divisors. There is a true Memory Bandwidth increase when running the exotic Divisors (Even for DDR-II 533 MHz Bus you are using an exotic Divisor) and you also have a performance increase.
 02/09/2007 07:03 PM
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Zozio
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He's thinking in terms of FSB where the maximum bandwidth of the memory (and therefore indirectly performance) is hindered when not running the ram 1:1 with the FSB however AMD's do not have this problem. I am not completely sure why this happens but I think its due to the onboard memory controller or HTT.

An example of what he is talking about is with conroes you have higher memory performance when running @ ddr2 533 than @ 667.

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 02/09/2007 07:15 PM
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Stix
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Ahh I get it now. I guess it can get a bit confusing.
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