building a new system... RAM question

[john2k]

Hi Everyone -

I'll be building a new system soon, right now I'm picking out the parts for it. So far I plan on buying an Asus A7N8X Deluxe & probably PC2700.

I'm trying to figure out how all the different speeds fit together - FSB, processor bus & RAM speed. I've been reading a lot of info online and still am not totally sure how the RAM speed factors into the equation.

The A7N8X motherboard supports FSB of 200/266/333. So that means the processor must have a bus of one of those speeds. Like the Athlon XP 1600 w/266Mhz bus or the Athlon XP 2800 w/333Mhz bus. The motherboard also supports PC2100, PC2700 & PC3200... this is pretty much where I'm a bit confused. PC3200 = DDR400, does that "400" also correspond to the FSB? Some of the info I read mentioned how the DDR speed is doubled or something like that. Does that mean DDR400 runs a FSB of 200Mhz? Or does DDR400 run at 400Mhz on the FSB?

Thanks in advance for helping me to understand all this.

John

 

[jlanka]

you got it right the first time. "Double" Data Rate is twice the bus speed. DDR400 == 200Mhz.

<i>It's always the one thing you never suspected.</i>

 

[john2k]

On the Asus website it says that the A7N8X Deluxe motherboard supports 333/266/200Mhz FSB. The page is at <A HREF="http://usa.asus.com/mb/socketa/a7n8x/specification.htm" target="_new">http://usa.asus.com/mb/socketa/a7n8x/specification.htm</A>

Does that mean it supports DDR666/DDR532/DDR400 or DDR333/DDR266/DDR200...?

 

[lhgpoobaa]

*sighs*
I really wish they wouldnt call it 333/266/200 fsb.

The <b>REAL</b> Mhz of the bus speeds are 166/133 and 100 respectivly. Its just that data is sent in packets TWICE per cycle, giving an effective speed of 333/266/200.

To squeeze the best performance out of the Nforce2 board generally its accepted that 2 sticks of PC2700 ram is best. PC3200 technically should be faster but:
A. the processor cannot make use of such bandwidth.
B. Ram runnign that fast usually uses more conservative memory timings for stability reasons, killing off performance.


<b>Just because someone's a member of an ethnic minority doesn't mean they're not a nasty small-minded little jerk. <i>Terry Pratchett</i></b>

 

[john2k]

Ok, so for example -

DDR333 = 166Mhz *2
333 FSB = 166Mhz *2

Is this the same with the processors? Is an Athlon XP 2800 with 333Mhz bus actually 166Mhz *2 also?

 

[lhgpoobaa]

PC2700 = DDR333 = 166mhz base speed.

Yes. the 333FSB XP's run at 166mhz.
That gives them better performance thanx to the greater bus bandwidth running synchronously with PC2700 ram.

<b>Just because someone's a member of an ethnic minority doesn't mean they're not a nasty small-minded little jerk. <i>Terry Pratchett</i></b>

 

[ddasilva]

Asus A7N8X Deluxe faster than the Gigabyte GA81HXP for less $$$? I dont understand the difference between RDRAM (1066) and how DDR333 mobo (asus) is almost as fast as the gigabyte mobo

 

[lhgpoobaa]

RDRAM has extreemly high bandwidth thanx to its dual channel nature.
The main disadvantages of RDRAM though is its high latency, compared to DDDR.


So thats why a well optimised DDR chipset can get so close to the performance level of a RDRAM one. Additionaly, the dependency of applications on memory bandwidth varies, so in some cases the difference between the two is less of an issue.


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[ddasilva]

"So thats why a well optimised DDR chipset can get so close to the performance level of a RDRAM one."

What motherboard/chipset is comparable to the Intel 850E? I am looking for a mobo that is close to the RDRAM speed in DDR...A replacement board for the Gigabyte GA81HXP board.

 

[dbw207]

Quick question, do you have to install DDR ram in pairs or can you mix it like 2 –128meg sticks and 1 - 512meg stick?

Arrg

 

[lhgpoobaa]

No, DDR goes in single sticks...
Unless you are running a Nforce, Nforce2 or Granite bay DDR chipset.

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[groth2757]

No, DDR goes in single sticks...
Unless you are running a Nforce, Nforce2 or Granite bay DDR chipset.

Am I correct in saying that one stick will still work? Though without the benefit of Dual DDR.

<font color=blue>Can anyone help me overclock my girlfriend's love toy?<font color=blue>

 

[knowan]

Yes you are correct. One stick will work, but 2 will work better. I'm not sure about the Granite Bay chipset, but with the Nforce chipset 3 sticks will work, but will be as slow or slower than 1 stick.

--------------
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[Crashman]

PC3200 should give you BETTER OVERCLOCKING OPTIONS, don't forget that some Athlons are already comming at DDR333 bus so that DDR333 memory doesn't have much room left.

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[lhgpoobaa]

Yes... you still can run single channel in those boards, but of course you loose dual channel goodness.

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[toss5000]

I would recomend getting PC-3200 (DDR400)(real speed of 200). I am aware that the PC-2700 (DDR333)(166 - real speed, you get the idea) performs better in the benchmarks. If you get the 3200 you can overclock better, and even run it at 333, to get the better performance. Plus once the barton core comes out you can sync the ram and the cpu fsb.

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[feidana]

I am also planning on purchasing a A7N8X-Deluxe within the next month or two. But I am also stuck on what memory speed to get. I am going to put a 2700+ which runs a FSB of 166. So I would think I would get the most performance out of my ram if I ran it at 166 as well (DDR333, PC2700).

How does that sound?

Also, I am kinda confused with dual-ddr support that the nforce2 has. A friend of mine tried to convince me that with dual-channel if i install two 256mb sticks, i only have 256mb of memory in my system, and that that is how dual-channel works. I argued with him but now I'm confused again.

Thanks, feidana.