cpu fsb bottleneck

[slyfox]

as the cpu fsb of a core2duo is 266x4=1066 mhz sum1 told me that getting a ddr2 ram with bus speed > 266x2 =533 mhz does not increase the performane.
is this true

 

[ashfame]

FSB: 1066Mhz It shows how fast the data can flow between PRocessor and Ram.
Ram frequency shows how fast it is able to provide data to the processor.
Acc to me: You are rght!
If you get a single stick of even 800Mhz, then RAM will not be able to provide enough data as much Processor can process it.
And if you got 2 ram sticks of >533 Mhz in dual channel then in that case fsb will be the bottle neck cuz Ram can provide data at greater rate than that fsb can take. Pl correct me if i am wrong.

 

[s18000rpm]

pls help me too

i have P4 3.06GHz proc. & RAM= 1GB (2x512) corsair DDR2 800 (runnin @533) & m/b= Intel 965WH.

when i'm playin games, the games run slower (lot of FPS issue in NFS Carbon).

in MW, the game randomly slows down, & Colin McRae05 also has major FPS issues (CMR05 is extremly low on resources, but on my system runs slow at evn 800x640resl.).

so can someone tell, do i have to get a C2D proc. to resolve this issue?

 

[ashfame]

ur processor has a fsb of 533mhz and so no use of running 2 sticks of 800mhz each in dual channel cuz even a single one will not b fully utilized.
A processor with high fsb 1066mhz n like wil provide u better performance.
Cant say anything specifically for your problem but increase in fsb wil surely give increased performance.

 

[s18000rpm]

so should i run RAM in non dual channel mode for time being?

or C2D is the ONLY answer?

 

[ashfame]

it doesnt matter for now that you run in dual channel or not. upgrading the fsb is the only answer. go for a c2d of 1066mhz fsb!
theoretically, running dual channel of 533mhz ddr2 will give you the same peformance as dual of 833mhz but practically it might give you some extra benefit. (cuz fsb is 1066mhz)
and pls also confirm for all this before u go out & buy hardware.

 

[slyfox]

check this out
*www.overclock.net/intel-cpus/146820-intel-overclocking-redefined-guide-successful-overclocking.html

 

[s18000rpm]

*s2.supload.com/thumbs/default/proc_temp.JPG
*s2.supload.com/thumbs/default/ram.JPG

is the ICH temp. ok at 67 degrees Cel.?

& the second pic shows at what timing the RAM is working.
i'm not able to increase the freq. to 667MHz even in User Defined mode. while setting, it changes to 667,but on next boot, it returns to 533

 

[Kniwor]

ok, firstly....

running memory 1:1 will give a better performance than nearby speeds not running 1:1, by that I mean If the processor has FSB 1066, and u're running a ram at 667Mhz, then it's better to run at 533 Mhz, but if u have a ram capable at 800Mhz, that will be faster then 533 Mhz overall.

Let me try and explain, take a ram at 533Mhz as a horse at certain speed that runs in perfect rhythm, then a ram at 667Mhz is a horse that runs faster, but topples at times and hence is slower overall, an 800Mhz ram is a much faster horse, so even if it topples, it's overall average speed is faster. (this is all considering FSB is 266Mhz). In short, running 1:1 always has an advantage.

So basically, the theory that "ram bandwidth will not be used" is not all correct, by that I man, if u put a faster ram in a processor with slower FSB, performance will increase, but might not be a big increase due to the FSB bottleneck.

But when u are buying a ram, it is always good to buy a faster one if the price difference is not much, I mean I just said 667Mhz is pointless on 266FSB processors, but I would still buy a 66Mhz, for many reasons, firstly, I might want to increase FSB.
Secondly, even if I'm not overclocking, I can always run the 667Mhz ram at 533Mhz with possibly better timings than a 533rated one would have done.

it doesnt matter for now that you run in dual channel or not. upgrading the fsb is the only answer. go for a c2d of 1066mhz fsb!
theoretically, running dual channel of 533mhz ddr2 will give you the same peformance as dual of 833mhz but practically it might give you some extra benefit. (cuz fsb is 1066mhz)
and pls also confirm for all this before u go out & buy hardware.

It does matter, as per all that I've said above
run it 800Mhz dual channel....

 

[deathvirus_me]

running memory 1:1 will give a better performance than nearby speeds not running 1:1, by that I mean If the processor has FSB 1066, and u're running a ram at 667Mhz, then it's better to run at 533 Mhz, but if u have a ram capable at 800Mhz, that will be faster then 533 Mhz overall.

Not exactly ... Yes , using a diff. divider than 1:1 definitely means that certain cpu cycles are lost ... but a few hundreds in a few millions doesn't actually put any noticeable impact on performance .. on any given day , even without proper tweaking .. ddr2-667 will perform the same if not better than ddr2-533 ... the former will infact offer much better mem. bandwidth ..

So basically, the theory that "ram bandwidth will not be used" is not all correct, by that I man, if u put a faster ram in a processor with slower FSB, performance will increase, but might not be a big increase due to the FSB bottleneck.

It'd be really hard to generalize this statement coz of the various combo's u can make between CPU's and RAM .. but considering the performance .. u'll have to consider many other aspects here too ..

In most general cases the statement that the total mem. bandwidth is not used up is pretty much correct .. albeit there are exceptions .. depends on the exact scenario of operation !!

as the cpu fsb of a core2duo is 266x4=1066 mhz sum1 told me that getting a ddr2 ram with bus speed > 266x2 =533 mhz does not increase the performane.

Ur friend actually is a bit confused .. he considers FSB Freq. and DRAM Freq. to be the same .. which is not .. both are specific to their components and are linked by a controller generally situated in the Northbridge .. So even though ur CPU FSB runs at a freq. of 266 (quad pumped) , u can put in any RAM as per the specs. of the supported modules in case of ur mobo .. which could be ddr2-400 , ddr2-533 , ddr2-667 , ddr2-800 etc. etc. .. In any case , to maintain a sync , a certain FSB : DRAM freq. ratio is maintained according to the combo u use ..

Like for 266 FSB , with ddr2 533 ram , the FSB : DRAM ratio will be 1:1 .. with ddr2-667 , it'll be 4:5 (simply 266/333) etc. etc. ...

 

[topgear]

@s18000rpm
Your board is based on intelG965 chipset and you're running games on your
mobos integrated graphics. So the ram speed reduced.
In the past issue of a digit mag I read someone had this kind of probelem. His 400mhz ram was running at 333mhz. the digits guys answer to this was the guy was using onboard vga so the ram speed reduced
I think you should use a graphices card to get the rams real speed.
correct me if I am wong

 

[deathvirus_me]

Huh ?? Never heard of this !! .. could be a bios issue ...

 

[Kniwor]

Not exactly ... Yes , using a diff. divider than 1:1 definitely means that certain cpu cycles are lost ... but a few hundreds in a few millions doesn't actually put any noticeable impact on performance .. on any given day , even without proper tweaking .. ddr2-667 will perform the same if not better than ddr2-533 ... the former will infact offer much better mem. bandwidth ..



It'd be really hard to generalize this statement coz of the various combo's u can make between CPU's and RAM .. but considering the performance .. u'll have to consider many other aspects here too ..

In most general cases the statement that the total mem. bandwidth is not used up is pretty much correct .. albeit there are exceptions .. depends on the exact scenario of operation !!



Ur friend actually is a bit confused .. he considers FSB Freq. and DRAM Freq. to be the same .. which is not .. both are specific to their components and are linked by a controller generally situated in the Northbridge .. So even though ur CPU FSB runs at a freq. of 266 (quad pumped) , u can put in any RAM as per the specs. of the supported modules in case of ur mobo .. which could be ddr2-400 , ddr2-533 , ddr2-667 , ddr2-800 etc. etc. .. In any case , to maintain a sync , a certain FSB : DRAM freq. ratio is maintained according to the combo u use ..

Like for 266 FSB , with ddr2 533 ram , the FSB : DRAM ratio will be 1:1 .. with ddr2-667 , it'll be 4:5 (simply 266/333) etc. etc. ...

I see u've DDR2 667, at the moement u are running the memory ~667Mhz 1:1 as I can see. Run a few memory benchmarks.

I would then suggest u to set the FSB to 266, and the memory to 333 using divider, and u will see that it's not the same.

If u were to run the FSB 266 24/7, it would have been more benificial for you to run the memory at 533Mhz and tighten the timings, rather than running it at 667Mhz. 1:1 has it's advantage, pls see benchmarks around.

And about the statement "ram bandwidth wont be used", I'm not generalizing, I'm saying it's NOT correct, sheesh, read properly man....

 

[deathvirus_me]

I see u've DDR2 667, at the moement u are running the memory ~667Mhz 1:1 as I can see. Run a few memory benchmarks.

I would then suggest u to set the FSB to 266, and the memory to 333 using divider, and u will see that it's not the same.

If u were to run the FSB 266 24/7, it would have been more benificial for you to run the memory at 533Mhz and tighten the timings, rather than running it at 667Mhz. 1:1 has it's advantage, pls see benchmarks around.

Hmm i tried all the settings before .. i think i remember some everest mem. read scores ..

ddr2-667 default - ~6500 (4:5)
ddr2-533 default - ~6100 (1:1)
ddr2-533 @ 4-3-3-10 - ~ 6600 (1:1)
ddr2-667 @ 4-4-4-14 - ~ 7100 (1:1)

I'd like to mention something here .. in the first two cases .. the ddr2-667 had higher latency .. while in the last two cases , for some reason the dd2-667 running at 4-4-4-14 has lower latency (hmmm , taking in account the increase in FSB) ..

Like i said .. 1:1 definitely has advantages .. but at a point where u run a different mem. divider , and use much tighter latency or more freq. on the Memory and the CPU , the divider won't make much of a difference .. but overall , its definitely recommended to run at 1:1 for best performance , particularly while oc'ing ..

And about the statement "ram bandwidth wont be used", I'm not generalizing, I'm saying it's NOT correct, sheesh, read properly man...

Didn't mean to offend you .. just added a bit of my opinion ..