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CPU Performance Ratios

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June 8, 2007 2:37:26 AM

Hi guys, need ur input on this one:

With the following Core 2 duos processors: E4400 (800 fsb); E6300 & E6340 (1066 fsb)

i would like to know what kind of DDR2 i need to use to achieve a Ratio of 1:1

example: would using Two pcs. of DDR2 (533 fsb) running on dual channel, achieve a Ratio of 1:1 with E4400?

what about the other processors?

thanks for your help.

More about : cpu performance ratios

June 8, 2007 3:02:54 AM

Why do you want to achieve a 1:1 ratio? You'll get better performance with a higher memory:FSB clock ratio.
June 8, 2007 3:29:10 AM

The E4400 runs at 200mhz, 1:1 for RAM makes for 400mhz DDR RAM. 266 E6300 and E6320 would run at 533 DDR RAM at 1:1.

The E6340, when it comes out (I think it's an upcoming chip), runs at 333 mhz, making 667mhz DDR RAM with a 1:1 ratio.
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June 8, 2007 4:13:45 AM

Quote:
Hi guys, need ur input on this one:

With the following Core 2 duos processors: E4400 (800 fsb); E6300 & E6340 (1066 fsb)

i would like to know what kind of DDR2 i need to use to achieve a Ratio of 1:1

example: would using Two pcs. of DDR2 (533 fsb) running on dual channel, achieve a Ratio of 1:1 with E4400?

what about the other processors?

thanks for your help.


I would recommend you getting 800Mhz RAM. So far not only 1:1 is reachable with OCing the CPU, but you can also take advantage of faster speed if you don't plan on OC.

Even if you try to run 667Mhz RAM with Core 2, its still slower than 800Mhz.

Trust me. I've done an experiment on that. :twisted:
June 8, 2007 4:56:44 AM

Quote:
Why do you want to achieve a 1:1 ratio? You'll get better performance with a higher memory:FSB clock ratio.


Isn't 1:1 the sweet spot for Core 2 Duo's?
June 8, 2007 5:51:31 AM

As with all things, it is a matter of balance.

The difference, except for a few games which are indeed bandwidth sensitive, between DDR667 and DDR800 on a Core2Duo is very small, typically a couple percent. (Athlon x2 chips by contrast show a performance delta of about 15% from DDR533 to DDR800)

So it boils down to price.

Right now the difference between DDR667 and DDR 800 is only a few $ per gig, so go for the DDR800.

On the other hand, DDR1066 is hugely more expensive than DDR800, and for 99.99% of the systems, buying more ram (ie 4 gigs versus 2) or a faster CPU grade would be a better use of the money.

For midrange Core2Duos and below, DDR800 or DDR667 are both solid choices.

Conroes respond more to latency and command rate than they do to absolute speed BTW, so a trick that often works is buy decent DDR800, run it at 667, but go with very aggresive timings/command rates.
June 8, 2007 6:10:09 AM

Yeah, that's what I thought... get DDR2 800 RAM, but run it at the FSB speed with tight timings rather than at 800MHz asynchronously.
June 8, 2007 6:23:13 AM

all u need is the bandwith between cpu to northbridge and memory to northbridge to be syncronous, ie for a cpu with an 1066 bus speed(266 quad data rate, 4 instructions per clock), the memory is only available at 533(266 double data rate, 2 instructions per clock), 667(333 double data rate), and 800(400 double data rate) speeds, so for the memory to match the cpu bus speed, u need 2 sticks of 533 memory running in dual channel effectively doubling to 1066 speed(4 instructions per clock).

using a faster memory would be a bonus as the cpu doesnt have to wait for the memory to catch up

so for your E4400 800fsb, your ok with 2 sticks of 533 memory, then later on u can upgrade to something like E6600 1066fsb dual core or even Q6600 1066fsb quad core without having to worry about your memory speed. using faster memory(667 or 800) would be a bonus but still u need 2 sticks for dual channel(effectively 4 instructions per clock)

___________________________
previous upgrade:-
P4 3.2Ghz 800fsb, intel 865PE mobo, 2x256Mb ddr-400 dual channel, nvidia FX5700 Ultra
current upgrade:-
P4 3.2Ghz 800fsb, nforce 650i SLI mobo, 2x 512Mb ddr2-533 dual channel, nvidia 7300GT
next upgrade:-
Core2 Duo/Quad 1066fsb, nforce 650i SLI mobo, 2x512Mb ddr2-533 dual channel, nvidia 7300GT
June 8, 2007 8:44:45 AM

Quote:
Why do you want to achieve a 1:1 ratio? You'll get better performance with a higher memory:FSB clock ratio.


ah bec i thought a 1:1 ratio would result in the most optimum performance.

with neither CPU and memory waiting for each other?

(i dont know if i'm right on this one though) :D 

correct me if am wrong.. thanks!
June 8, 2007 8:49:16 AM

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Quote:


I would recommend you getting 800Mhz RAM. So far not only 1:1 is reachable with OCing the CPU, but you can also take advantage of faster speed if you don't plan on OC.

Even if you try to run 667Mhz RAM with Core 2, its still slower than 800Mhz.

Trust me. I've done an experiment on that. :twisted:


ah ur saying i should get a DDR2-800 in dual channel? (sorry nob, just to clarify)

am not planning on OC..

can u give a percent increase difference when using DDR2-800 vs DDR2-667? (am assuming this is in dual channel)

wat processor did u use in the experiment?

thanks! :D 
June 8, 2007 8:54:29 AM

Quote:
As with all things, it is a matter of balance.

The difference, except for a few games which are indeed bandwidth sensitive, between DDR667 and DDR800 on a Core2Duo is very small, typically a couple percent. (Athlon x2 chips by contrast show a performance delta of about 15% from DDR533 to DDR800)

So it boils down to price.

Right now the difference between DDR667 and DDR 800 is only a few $ per gig, so go for the DDR800.

On the other hand, DDR1066 is hugely more expensive than DDR800, and for 99.99% of the systems, buying more ram (ie 4 gigs versus 2) or a faster CPU grade would be a better use of the money.

For midrange Core2Duos and below, DDR800 or DDR667 are both solid choices.

Conroes respond more to latency and command rate than they do to absolute speed BTW, so a trick that often works is buy decent DDR800, run it at 667, but go with very aggresive timings/command rates.


thanks for the reply. i am assuming that all the DDR u mentioned are in DDR2 right?

when u said " but go with very aggresive timings/command rates." do you mean OC the memory? or is this just setting the timings? (sorry nob)

thanks! :D 
June 8, 2007 8:59:15 AM

Quote:


so for your E4400 800fsb, your ok with 2 sticks of 533 memory, then later on u can upgrade to something like E6600 1066fsb dual core or even Q6600 1066fsb quad core without having to worry about your memory speed. using faster memory(667 or 800) would be a bonus but still u need 2 sticks for dual channel(effectively 4 instructions per clock)



ah so the purpose of getting a faster memory timing than the CPU, is for future upgrades? so that u can still use it when u change ur CPU?

just a clarification: how can using faster memory (667 or 800) be a bonus when the max fsb of cpu is just 1066 (for the E6300)? how can the cpu take advantage of the extra bandwith? (sorry nob)

thanks! :D 
June 8, 2007 2:42:56 PM

The biggest advantage for using faster memory IMO is that you can tighten the timings when you drop the FSB. For instance my memory is PC6400 (DDR2 800) with timings 5-5-5-15-2T @ 400 (SPD rating) and @ 266 mhz (DDR2 533) 4-4-4-12-2T at stock voltages. When i overclocked my CPU to a FSB of 333Mhz I synched memory also at 333(DDR2 667), raised memvoltage and was able to tighten mem timings to 4-4-4-12-1T. These timings,for me at least, only work when mem is at 333. If i raise the FSB more i will have to loosen timings and for me the increased speed in Mhz does not make up for the loss in timing. This depends on how you measure it i suppose and what app's you'll be running so for you it could work out the other way around. I think this largely depends on how much of a FSB gain you can achieve without dropping timings.
If you're not going to overclock I guess the best thing for you would be to go with the 1066 FSB cpu, underclock some decent PC6400 memory @ 266 and drop those timings.

GL
June 8, 2007 4:33:16 PM

Quote:

ah so the purpose of getting a faster memory timing than the CPU, is for future upgrades? so that u can still use it when u change ur CPU?

just a clarification: how can using faster memory (667 or 800) be a bonus when the max fsb of cpu is just 1066 (for the E6300)? how can the cpu take advantage of the extra bandwith? (sorry nob)

thanks! :D 


if u look at me im running an old Pentium4 with 800 fsb at 3.2Ghz, my memory is ddr2-533 and running in dual channel(effectively 1066) which is the slowest ddr2 memory available, and ive got headroom when i upgrade to a core2 duo or quad in the next month as i dont have to change memory when i upgrade the chip(dont forget cpu does 4 instructions per clock and memory does 2 instructions per clock)

having faster memory means cpu doesnt have to wait to get data from memory
June 9, 2007 6:59:57 AM

Quote:
ddr2-533 and running in dual channel(effectively 1066) which is the slowest ddr2 memory available


DDR2 -533mhz is 2nd slowest ddr2 ram. The slowest is DDR2 3200 or 400mhz.

By the way, if you run 800mhz 5 5 5 15 with 3:2 memory ratio, 3 being the Ram and 2 being the FSB, the memory will be faster than running 533mhz 3,3,3 8with 1:1 memory ratio.
June 13, 2007 3:53:16 AM

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Quote:

By the way, if you run 800mhz 5 5 5 15 with 3:2 memory ratio, 3 being the Ram and 2 being the FSB, the memory will be faster than running 533mhz 3,3,3 8with 1:1 memory ratio.


if running a memory with 3:2 ratio, is faster than running 1:1...

would this affect the overall performance of the computer? since the cpu is still only running at 1066?

thanks!
June 14, 2007 6:56:27 AM

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Quote:

By the way, if you run 800mhz 5 5 5 15 with 3:2 memory ratio, 3 being the Ram and 2 being the FSB, the memory will be faster than running 533mhz 3,3,3 8with 1:1 memory ratio.


if running a memory with 3:2 ratio, is faster than running 1:1...

would this affect the overall performance of the computer? since the cpu is still only running at 1066?

thanks!
It's faster, though on the order of a few %.
http://www.xbitlabs.com/articles/memory/display/core2du...
June 19, 2007 8:11:39 AM

a few percent?

i guess this would mean if price is almost the same... go for higher memory fsb? :D 
!