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FSB Question

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April 10, 2004 4:56:07 PM

I just ran 3DMARK2001SE and the results said my FSB was 167Mhz. I have an athlonXP 2500(333). My mobo is nforce2 400ultra chipset with 400Mhz FSB. My memory is corsair XMS DDR400. Can anyone explain to me why it was saying 167?

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April 10, 2004 5:57:08 PM

well, it has been rounded, because it might be around 166.66, or something like this. And 166 MHz is the frequency, and since the bus is DDR, which mean Double Data Rate, it fit with your CPU bus which is 333(166 X 2). The memory bus, run at DDR400 (200MHz X 2). The memory bus is not in sync with the FSB, which mean that your system might not run at it optimal speed. In the bios, you can either raise the CPU FSB too 200 (2500+ is 11x166=1.83 GHz and with FSB at 200, that give you 11X200=2.2GHz, same as 3200+. 11 is the multiplier) to have it run in sync with the memory bus, but maybe you'll have to tweak your setting a bit. This is overclocking. If you are not used to that, I dont recommend that until you read and become familiar with the notion of overclocking. You can easily overheat your CPU. New 2500+ has the multiplier locked so you cannot lower the final clock if it get too hot (exemple, too hot at 11X200, you can try 10x200=2.0GHz (3000+) or 9.5X200=1.9GHz).But you can lower the memory bus to 166, still in bios, to have it run in sysc with the FSB. This might remove latency and improve performance. Just test your computer with the different setting and use the one that give you the best performance.

-Always put the blame on you first, then on the hardware !!!
April 10, 2004 10:15:58 PM

On Athlon XP's the FSB is double-pumped, so for you, the effective FSB would be 333. On Pentium 4, say, the newer "C" versions, the FSB is quad pumped. The FSB is 200 mhz but it is effective 800 mhz, and that is what it says on the box.

"640K oughta be enough for anybody." - Bill Gates
That'll be enough L1 cache for me too...
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a b V Motherboard
April 10, 2004 10:36:06 PM

No pumping, humping, or any other sexual inuendo, it's Double Data Rate, so a 166MHz clock rate provides a 333MHz data rate. See how data rate explains everything and humping is something you see on the Discovery channel?

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April 11, 2004 2:49:04 AM

I went into my bios and checked my memory freguency. Its running at 400Mhz. Now that is the same as my FSB, right? My processor is set at 166. So when running the 3dmark it should show 400 instead of 167 right?
a b V Motherboard
April 11, 2004 3:26:21 AM

Actually no. FSB (Front Side Bus) used to refer to the entire CPU to RAM bus frequency, but for several years now chipsets have been on the market that divide that into the CPU bus and Memory bus with the ability to run those at separate speeds. The CPU bus is now refered to as FSB.

Your CPU bus is running 167MHz, but your RAM bus is running 200MHz. Now, 200MHz clock is 400MHz data rate and it can be refered to as either 200 or 400 depending on software. Your CPU bus clock is 167MHz, which has a data rate of 333MHz.

The only way you're going to see your CPU bus (FSB) at 200MHz is by overclocking.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>
April 11, 2004 7:03:15 AM

I'm truly sorry dear Crashman:the RAM bus frequency on the chipset for AMD cpu cant go under the FSB.So you can only set the RAM bus frequency to 266 or more than,when you use the 266MHZ FSB.^_^

Truth is somewhere out there!
--Movie 'X Files'
a b V Motherboard
April 11, 2004 7:08:04 AM

who the hell are you and why the hell don't you read before spilling out such crap? d00d, he's running a 166MHz processor bus and at best a 200MHz RAM bus, that's DDR333 for the CPU and DDR400 for the processor. AMD advertizes CPU bus speed in DDR just like Intel advertizes it in QDR. Who the hell said anything about running the RAM slower than the CPU? Last time I looked at a math book 166 is less than 200.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>
April 11, 2004 7:19:04 AM

O_oMy mistake.I'm sorry to make you furious.But please do more attention to your words.

Truth is somewhere out there!
--Movie 'X Files'
April 11, 2004 6:28:53 PM

So, if I wanted to get the most out of my system I need to upgrade to an athlonXP 3000 or something thats got FSB of 400? That way everything is running at 200Mhz, right? I set my FSB to 200Mhz when I first put this together and it ran stable for a few minutes but then just crashed. If I wanted to overclock, whats the best cooling fan? I really don't want to go to water cooling. Thanks for your help guys. I learn something new every day.

<P ID="edit"><FONT SIZE=-1><EM>Edited by HellRazor on 04/11/04 02:30 PM.</EM></FONT></P>
a b V Motherboard
April 11, 2004 9:27:16 PM

Yes, if you want the most out of your system you'll want to run 200MHz FSB (aka 400 bus), such as the second 3000+ or the 3200+. But your 2500+ is known to usually run stable at 200MHz FSB, so you might just want to ask the guys in the CPU's Overclocking forum exactly what to do to get a stable 200MHz FSB overclock (which makes your CPU 3200+ speed) without increasing noise substantially.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>
!