I need some guidance re: FSB's

Helium_Junkie

Helium_Junkie

Helium_Junkie

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The hardware:

C2D E4400 2.0GHz
Cruicial Ballistix DDR2 PC5300
Asrock Quad VSTA

I am a little unsure about some of the options on this board. I have found the CPU FSB option, and raised this from 200 to 270.
But when I find the memory option it gives me some set choices, I think they were 200,266,333. Do I need to set this to some kind of ratio amount with the cpu FSB? I don't know what the best setting to use is. PC5300 is 333MHz right? :confused: Will this adjust itself to what my CPU is set to?

I cant remember what I chose, I think I left it where it was, but in CPU-Z the memory speed was displaying as the same frequency as the CPU: 270. Is that right?
On the CPU tab the FSB was showing as 270, but then at the bottom of the page there was a frequency stated as being over a thousand... is that also right? Is there a limit I should not cross?

Any advice most appreciated!
 
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OK 1st thing 1st, Intel fsb is quad-pumped so the actual fsb is 200Mhz (default for your chip) while the effective fsb is 800Mhz, so if you increase it to 270 the effective speed will naturally be 1080.

At the moment your RAM is running 1:1 with the fsb and you should keep it that way if you intend to overclock it further. Once you found the maximum oc for your CPU you can start setting higher ratio to make your RAM run faster than fsb.
 
Helium_Junkie said:
Is the memory FSB also quad pumped? So a 270 ram fsb = 1080 also? :eek:
Click to expand...

Helpfully, it is doubled - 333MHz = 667 MHz DDR :D

So if you have your FSB and RAM both at 333, and assuming it all posts, then your CPU will be running at 3.33GHz and your RAM will be at 667MHz DDR, (i.e. at stock settings)
 
steve258 said:
Double Data Rate so your ram is currently running DDR2 540.
Click to expand...

Right! :) Thank you for your help so far :)

So, I have the ram and cpu at 200 stock, and up the cpu to 270 - which brings the ram up to 270 also (ddr540).
My ram is faster than this though, so should I set the ram to be 333?
Is a 200CPU and 333RAM compatible?
And then when I up the CPU to 270, will the ram go up with it to 403?

Or should they both be the same FSB?
 
As said if you wish to oc your CPU further you should leave it as it is for now as you will need some headroom on RAM for raising the FSB, so you can oc your chip to 3.33Ghz (FSB:RAM = 1:1 333Mhz:333Mhz DDR2 667) without overclocking your RAM as pointed out by melbourne720. Although it is very unlikely for your mobo to reach anything over 300Mhz fsb.

Not sure exactly how the RAM options work on your mobo so the best thing to do is to try different settings and use CPUZ to determine your RAM speed with different ratio options, but whichever ratio you use RAM speed will ALWAYS increase with FSB apart from some Nvidia chipsets where you have the option to run your RAM "unlinked" with FSB.

*EDIT* just noticed you have the ballistix PC5300 which is a great clocker, well known for achieving well above DDR2 1000 with the right settings and voltage.
 
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I dont think the mobo can physically go past 300, but I am happy with 270-290.
So for this setting, I could quite reasonably select a different MHz for the ram until it was over 667, even if the CPU didnt rise with it?
Is there any reason to choose a ratio other than 1:1? Will doing this actually give a performance boost?

So as an example:
CPU @ 270MHz
RAM @ 333MHz (which gains the 70 from the cpu rise, and is then doubled because it is DDR, bringing it to 806MHz)

Is that correct and feasible?

I really do appreciate your help, this is all quite mindboggling for me and working with examples is the easiest way for me to get my head around it.
 
wooah there, your memory is just DDR, so what ever the memory speed is set to then double that number. In your example, the memory would be at double 333MHz = 667MHz.

There will be a ratio of FSB to memory speed, which means that your memory speed might be something other than 333MHz. But whatever the number is, then just double it. e.g.

FSB = 270
FSB:RAM ratio = 1:1
RAM = 270 x 2 = 540MHz DDR

or

FSB = 270
FSB:RAM ratio = 2:3
RAM = (270 x 3/2) x 2
= 405MHz x 2
= 810MHz DDR
 
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There doesnt appear to be an actual ratio option, just the speed as a setting of either 200, 233, 266, 333 etc.

But with the speed set to 200, and the cpu to 270, cpu-z lists the ram as being 270, so i assume this number should be considered as the ratio to the stock cpu speed :confused: in which case 333 = a ratio of 3:5...?


Also, is it worthwhile changing this ratio? i.e. having a fsb on your ram higher than your CPU. Is there any point to doing so?
 
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Helium_Junkie said:
So as an example:
CPU @ 270MHz
RAM @ 333MHz (which gains the 70 from the cpu rise, and is then doubled because it is DDR, bringing it to 806MHz)

Is that correct and feasible?
Click to expand...

I calculated 450Mhz DDR2 900 :-/

I don't think it works by simply adding the 70Mhz on top - if it's running on ratio basis then the RAM increase will be greater than FSB e.g. if you are running 2:3 FSB:RAM ratio then there will be 1.5Mhz RAM speed increase per FSB increase.

RAM options differ from mobo to mobo so I can't say for absolute certainty. The best thing to do is try 333Mhz option and see what your RAM is running at in CPUZ and work out the FSB:RAM ratio for that option.
 
Ah, I see your point on the +70 being incorrect, makes sense.
Well, I will try when I get home and see what happens! Thank you all for trying to explain this to me :D Expect a "Oh no I broke it" thread tomorrow :p

:)
 
I'm in the saem boat as you, but instead of the e4400 (i wanted to buy it, but had to save a few £ for my daughter's first birthday) I got the e2160...and I only have pc3200 ram...but i've got the FSB up to 290, but my ram speed is 181...my timings are low (2.5-3-3-7) but i'd like to get the ram up to 200MHZ. Right now my ram is set at 166Mhz; i'm afraid if I set it to 200Mhz, it'll get set too high and kill my ram...
I reckon my best bet would be to keep it set at 200Mhz with 200Mhz FSB and raise the FSB until it clocks the ram too high? is that what you guys recommend?
 
So is there a magic ratio with these new fangled intels then? Or is it best to run ram at it's highest Mhz, then FSB at it's highest, then find the closest ratio?
 
melbourne720 said:
Don't think so.
Click to expand...
I'm pretty sure it is best to run in a 1:1 ratio, as there are no lost cycles. Obviously the C2D's can overclock more than your ram though so it's probably best to think about it as efficiency rather than speed. If you run your ram and FSB on a different ratio, you can probably get your CPU higher, and have more power, but it'll be less efficient if you get me.
 
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