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New to the P4 DDR scene, quick question?

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KrazyKevin

New Member
Joined
Feb 19, 2004
I just bought me a P4 2.8c, P4P800 deluxe and 2 x 512 Geil value PC3200 memory. This is my first attempt to o/c a ddr board/memory. On my old PC100 systems it was as simple as for instance:

PIII 700 = multiplier of 7 x FSB of 100 = 700. Raise FSB to 105 and you get 735mhz.

I'm not understanding the the ratios on my new board. I have the FSB speed and then the ratio. This is confusing me. I don't understand what the ratio does. Can someone please just give me a few examples of a 1:1 o/c vs. a 5:4 or a 3:2. It would be greatly appreciated.

Yeah I know, I need better memory. But, its gonna have to do for now. Thanks in advance.

Kevin
 
1:1 - 400 mhz
5:4 - 333 mhz
3:2 - 266 mhz

ur using geil, like i do, make sure u raise ur vdimm at least 2.7v

gd luck!
 
I still don't understand what the numbers in the ratios represent?
And also, what does this get you by using the other ratios besides 1:1?
 
Your new system works the same in regards to CPU speed setting:

Multiplier x FSB = CPU speed (i.e. 14 x 200 = 2800 or 2.80C)

Now with the high bus speeds on intel systems we needed some way to run the memory in spec as well. So say you own pc2700 memory which runs at a speed of 166 X 2 = 333 MHz. You need to take your FSB of 200 and switch it to 166 for the memory thus the reason for the memory ratios.

As in the PC2700 example above your CPU FSB is 200 and when you use a 5:4 ratio yor memory speed is 160 MHz:

200 / 5 = 40 X 4 = 160 x 2 = 320 = memory in spec.

If you owned pc2100 memory use the 3:2 ratio:

200 / 3 = 66 X 2 = 133 x 2 = 266 = memory in spec.

Now lets look at overclocking. Say you have a 2.40C that can run at a FSB of 300 for a CPU speed of 3.60 GHz. Now they have not made memory that can run at 300MHz which would be an actual of DDR600 (300MHz X 2). But they do make memory that can run at 250MHz or DDR500 (250 X 2). So in this case we would use the 5:4 ratio:

300 / 5 = 60 x 4 = 240 x 2 =480 = memeory in spec.

Hope that helped :)

M.
 
Thank you very much. Thats exactly what I needed. But this don't effect anything? Whats more important, having my fsb a little lower cause me memory can't handle it, or slowing my memory to get a little more on the fsb? Lastly, my ram timings for my geil value is 2.5-6-3-3 from their website? What should I do to these numbers, should I try to move em? Thanks again M. Ham
 
raise the vdimm to 2.85 and then start tightening those timings to like 2-3-3-5 burst 8 or maybe even try 2-2-2-5 burst 8 if unstable with the last numbers go to the first suggestion.mam enabled
 
KrazyKevin said:
Thank you very much. Thats exactly what I needed. But this don't effect anything? Whats more important, having my fsb a little lower cause me memory can't handle it, or slowing my memory to get a little more on the fsb? Lastly, my ram timings for my geil value is 2.5-6-3-3 from their website? What should I do to these numbers, should I try to move em? Thanks again M. Ham

With timings like your memory has you are probably better off trying to raise FSB and use the 5:4 ratio. You don't have much room to lower the timings and try to run a 1:1 ratio. Concern is that at say a 230 FSB and a 1:1 ratio you would need to lower you timings to 3,4,4,8 or similar.

Most benchmarks show that a high FSB combined with a 5:4 ratio and low timings (2,2,2,5) and a lower FSB but a 1:1 ratio and higher timings (2.5,3,4,6) are about the same (synthetic applications notwithstanding).

My suggestion would be to enable the 5:4 ratio and then start bumping the fsb up. This way your memory "should" not be the limiting factor (if you hit 250 FSB without breaking a sweat then you are going to have to look at the memory sub system a little closer). Chances are with stock cooling you can hit between 215 and 235 with you memory running around 170-190 MHz. Once you determine what your processor can do, then you can move on to seeing if you can lower the memory timings. Rough guess is with a litle bit more voltage (1.75V) you might be able to run your memory 170-190 MHz with 2,6,"2-3","2-3" timings (I cannot tell what order Geil state there memory timings, thus the "2-3").

Refer to http://www20.tomshardware.com/motherboard/20040119/index.html for more info on timings and their importance.

Anyways goog luck :)

M.
 
Right now I"m at 5:4 ratio, fsb at 250, P4 2.8c @ 3.5ghz. My memory settings are 2-3-3-5 burst 8. MAM enabled and that other setting is on turbo, sorry i forgot the name of the setting. My cpu temp from the asus probe utility idles around 30. 30 mins of the new UT2K4 demo gets it up to about 37c. What should I do from here? All this on stock cooling.
 
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keep upping the fsb.if it gets unstable you will have to sacrifice your tight timings.run your vdimm at 2.85 and vcore at 1.6 and up that fsb!!!hehehe
 
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