# Thread: I don't get this FSB:DRAM Ratio 1:1 stuff???

1. ## I don't get this FSB:DRAM Ratio 1:1 stuff???

ok, so i hear lots of people saying you should have a 1:1 ratio, between the cpu frequence any the ram frequency so that one of them is not the bottleneck ( i think )

and so i opened up cpu-z and it says i have 5:6
but how do i work out, what frequencys i need for a 1:1 ratio?
my motherboared does not have an opetion for it ( all it has is ' memory SPD )
so is there like a forumula ? or am i just missing something realllyyyy simple

( i normally run my q6600 at 3.2 or 3.3.....if that helps...so what ram frequency would i need for 1:1)

any help would be much appriciated ( i have tried google but no one is "explaining it"
thanks!

2. In other words, you don't want to multiplier to make up any difference in speed. For example, if your RAM is 100Mhz, you would want your CPU to be something like 100Mhz x 10 = 1Ghz, not 50Mhz x 20 = 1Ghz. So you want FSB to match the frequency of your RAM. I've been out of the loop for quite a while, so I can't help you with your specific example, but that is the basic idea.

3. With a clock speed of 3.2 GHz (400 MHz x 8), set the System Memory Multiplier to 2.00. So with an FSB of 400 MHz (CPU Host Frequency), CPU Clock Ratio at 8x, and DRAM Multiplier at 2.00... you end up with a 1:1 ratio (333/667 NB strap; 800 MHz effective DRAM frequency.) Using a 5:6 divider (333/800 NB strap) with the same 400 MHz FSB, you would end up with a resulting 960 MHz DRAM freq. So if you're running PC2-6400, and the RAM is rated at SPD timings of 4-4-4-12-2T at 800 MHz, you would use the 1:1 divider at a 400 MHz Host freq. If running on a 5:6 divider, the resulting DRAM freq. of 960 MHz would require you to loosen the timings to something like 5-5-5-15-2T; with possibly higher Vdimm and / or vNB (vMCH.)

4. I never do the math and get mine to 1:1 I guess

Hehehe

Might have to explore that one soon for hell of it.

5. I'm similarly confused. I am just now getting into overclocking and apparently, i've been running with a 3:5 ratio for the past 2 years without overclocking anything.

I'm in the process of OCing my Pentium D 940 presler from 3.2 to 3.8 (200x16 -> 238x16)
my ram is 2 gigs of dual channeled ddr2 667 what should i change in my settings to so that my ratio is better.

6. i think basically, if you have ddr2 ram
your cpu frequency ( in your case 238) should be the same as half the ram frequency

so if you have ddr2 ram, at 800mhz
for a 1:1 ratio, you need a 400mhz cpu frexenct ( x watever multipler )

so psywold, for you
for a 1:1 ratio, u need to have a 333 x ( whatever multiplier )

and if i have ddr2 1000mhz ram, then for a 1:1 ratio, my cpu frequency should be 500 x Z
with Z being the multiplier

right?

7. Perhaps a better way to explain it is, if you have an 800FSB CPU (200mhz base clock), you'd want your RAM set to DDR2-400 (200mhz base clock). Then with the CPU at 238mhz, on the same RAM setting, the ram would be running at 476. A 1066FSB CPU would use a 266mhz base clock, and DDR2-533, etc.

Honestly, though, I wouldn't try too hard to get it running 1:1, you don't really gain anything by running the RAM faster, but you don't really lose anything either. It only becomes an issue when you're overclocking, and a higher RAM ratio is pushing the RAM higher than it can handle.

8. Ok that clears things up a bit. It looks like i can't change the multiplier on my processor anyway. If i'm understanding this correctly it means that i can't really do much to balance ratio even if i still wanted to. I can change the system memory multiplier. what would that do?

9. Running 3:4 ATM seems to be working out pretty well still playing with things

10. Originally Posted by Old Thrashbarg
you don't really gain anything by running the RAM faster, but you don't really lose anything either.

11. You're better off IMO running the fastest ram you can on the fastest FSB you can. That's just me though.

12. fast ram is good if you have a board and cpu that can go pretty far fsb wise. i.e. if you have some pc8500, and you can run your board at 533fsb, your ram would be at stock speed, that would be at 1:1. but say youve got a quad and there is no chance for you to make it that far, but you can do 450fsb with no problem, provideing your ram will go that fast, you can use a 4:5 divider and run your stix at around 565mhz (ddr2 1135). you wouldnt make nearly the same bandwidth that you would have with the shear mite of fsb, but the faster ram speed would help keep your latency down. so in a nutshell, id rather run 600mhz cas5, over 500mhz cas4

13. Originally Posted by freeagent
you wouldnt make nearly the same bandwidth that you would have with the shear mite of fsb
The high FSB is fine (and desirable), but the processor clock speed is the key to speed. If you need to drop the FSB some (not too far) and can raise the multi and OC the RAM, you MAY get better results. Like this

My old way still works better:

14. @18 is # 1
Sandra numbers != actual performance in applications. A couple hundredths of a second difference in SuperPi shows that pretty well, I think.

15. Originally Posted by 18 is # 1
The high FSB is fine (and desirable), but the processor clock speed is the key to speed. If you need to drop the FSB some (not too far) and can raise the multi and OC the RAM, you MAY get better results. Like this

My old way still works better:

i tried 4700mhz, but did not see any difference

http://www.xtremesystems.org/forums/...postcount=2655

16. Since mine is running at stock 533 x2 = 1066mhz CPU-Z dosn't show my memory correctly thinks it's PC6400 Kingston type yet it does show the correct timings I am using which is 5-5-5-15 20 2T settings it reports my FSB/DRAM at 3:8 not sure if this is correct.

Memtest through DOS at start up will not work with any setting on this Kingston brand not at auto or manaul to what I am set now yet Windows XP, playing games, creating DVDs or converting music has not brought a BSOD yet.

17. Originally Posted by AngelfireUk83
Memtest through DOS at start up will not work with any setting on this Kingston brand

18. Originally Posted by Old Thrashbarg
@18 is # 1
Sandra numbers != actual performance in applications. A couple hundredths of a second difference in SuperPi shows that pretty well, I think.

19. Wow, hadn't tried the Linpack before but must not be doing something too off got through em on standard, albeit at 88C sometimes.

Have that True copper coming then I can stress thing out more once again

I just can't run this quad at those settings to get it there. Like Freeagent said, about 450X9 about tops I can get out of this thing currently, but the OCZ does 1200 there on really tight settings.

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