FSB 1066MHz with DDR2 800 or DDR2 1066

[Dovii]

Background

First, please forgive the following noob questions, but this is my first build and I don't want to goof it up...

I bought a E6600 through Tigerdirect and it shipped already. =)
It has 1066MHz FSB

I was planning on getting the ASUS P5W DH Deluxe as it seems to be the MB to get right now for C2D (according to reviews). It supports up to 1066MHz FSB, but appears to only offer support up to DDR2 800.

Questions

1. Is it not best to have your memory clocked the same (synchronized - 1066MHz FSB with DDR2 1066) with your FSB? For example - my barton 3000 has 333MHz FSB and I run PC2700 ram with it.

2. Will the ASUS P5W DH Deluxe support DDR2 1066?

3. Are there any C2D platforms that support DDR2 1066 available yet?

4. Should I hold off on purchasing a MB until an appropriate one is available?

Thanks for the help,
Nate

 

[xxsk8er101xx]

to my understanding the memory isn't tied to your fsb and has multipliers like 2/1, 1/2 and so on.

I bought DDR2 675 and it'll work ... if you read the one article i think its on anandtech.com it shows the performance differences from 667 to 800 to 1066 http://www.anandtech.com/memory/showdoc.aspx?i=2800&p=6

Background

First, please forgive the following noob questions, but this is my first build and I don't want to goof it up...

I bought a E6600 through Tigerdirect and it shipped already. =)
It has 1066MHz FSB

I was planning on getting the ASUS P5W DH Deluxe as it seems to be the MB to get right now for C2D (according to reviews). It supports up to 1066MHz FSB, but appears to only offer support up to DDR2 800.

Questions

1. Is it not best to have your memory clocked the same (synchronized - 1066MHz FSB with DDR2 1066) with your FSB? For example - my barton 3000 has 333MHz FSB and I run PC2700 ram with it.

2. Will the ASUS P5W DH Deluxe support DDR2 1066?

3. Are there any C2D platforms that support DDR2 1066 available yet?

4. Should I hold off on purchasing a MB until an appropriate one is available?

Thanks for the help,
Nate

 

[chuckshissle]

The 800 should be good enough but if can afford 1066 then its better.

 

[weilin]

Ok the e6600 has a 1066 Bus. the ram "required" for it is really ddr2 533 as ddr2 533 in dual channel operation runs at 1066 mhz. Recommended ram would be DDR2 667 thus giving you tighter timings. DDR2 800 and above are for overclockers who wish to push the fsb from 266 to up around 330s and higher.

 

[chuckshissle]

Yeah that's what I mean if you can afford the 1066 then that would be good. I'm using 533 myself which is perfect for my 840 when it comes to overclocking.

 

[Dovii]

Ok the e6600 has a 1066 Bus. the ram "required" for it is really ddr2 533 as ddr2 533 in dual channel operation runs at 1066 mhz. Recommended ram would be DDR2 667 thus giving you tighter timings. DDR2 800 and above are for overclockers who wish to push the fsb from 266 to up around 330s and higher.

I thought ddr2 533 ran at 266mhz x 2 and to sync up with the FSB@1066 you would need to run your memory at 533mhz at dual data rate = ddr2 1066. Isn't the whole point of SDRAM ("S" = sync) to run the memory at the same frequency as the system bus...

Now I'm confused.

 

[xxsk8er101xx]

for ddr the highest speed is ddr 400. right?

You put ddr-400 in 800mhz fsb right?

ddr-400 ='s 800mhz right?

ddr2-533 ='s 1066mhz right?

what's the problem?

Ok the e6600 has a 1066 Bus. the ram "required" for it is really ddr2 533 as ddr2 533 in dual channel operation runs at 1066 mhz. Recommended ram would be DDR2 667 thus giving you tighter timings. DDR2 800 and above are for overclockers who wish to push the fsb from 266 to up around 330s and higher.

I thought ddr2 533 ran at 266mhz x 2 and to sync up with the FSB@1066 you would need to run your memory at 533mhz at dual data rate = ddr2 1066. Isn't the whole point of SDRAM ("S" = sync) to run the memory at the same frequency as the system bus...

Now I'm confused.

 

[weilin]

edit: see post below

 

[Dovii]

Thanks for clearing that up!

 

[second_derivative]

Today pairs of DDR SDRAM are run in whats called dual Channel. Ram is usually advertised with its single channel speeds (DDR2 533 is 533mhz by itself). If you put 2 sticks of that ram together in a dual channel capable board you will get Dual Channel Operation or 533x2 or 1066.

i disagree, to my understanding it works like this: the processor gets a "system" clock 266MHz (the FSB is quad pumped making the effective bandwidth 266Mhz*4=1066MHz),

your DDR SDRAM receives this same "system" clock (assuming 1:1 divider), but due to the Double Data Rate (transfer on rising and falling edges of the clock) the effective clock is 2*266MHz=533MHz.

a single channel of ram has a 64-bit interface to the FSB so the data transfer rate is 533Mhz * 64-bit data bus * 1byte/8bits = 4200 MB/s thus the PC2-4200 rating.

when you use a pair of modules and run dual-channel configuration you effectively increase the width of the databus to 128 bits, thus doubling your data transfer rate. i'm emphasizing that your effective clock has not changed, though your performance improved greatly.

now, why would you need RAM faster than DDR2-533 with a 1066 FSB? say your processor has a locked multiplier and you want to OC. you can do this by increasing the "system" clock from 266MHz to say 300MHz (thus increasing the FSB). your cpu's effective frequency is now multiplier*300MHz.

if you wish to keep your RAM synchronized with your FSB (keeping the divider at 1:1) your effective memory clock will be 2*300MHz = 600Mhz or DDR2-600. Needless to say if you try to OC DDR <600 you may need to relax the latency timings. but if you have, say, DDR2-800 you can easily increase your "system" clock to 400MHz without (theoretically) having any instability issues with the RAM. there are two ways i know to prevent such instabilities 1) loosen timings, 2) set the divider to 4:3, 2:1 etc. for system to RAM clocks. it seems to me that generally 1:1 ratio is what people strive for, though personally i cannot offer any opinion on the performance difference. (can anyone explain the advantage of one over the other?)

if anything i said is wrong please correct me, after all i'm just learning this too. also, a question for the more knowledgeable: what's more important the CL timings or RAM bandwidth, for example comparing DDR2-667 CL4 to DDR2-800 CL5?

 

[weilin]

ur right, i was just trying to keep it simple and left out a few details. I did a full explaination on other posts and it just got ppl really really confused. anyways Latency wise, Intel isnt very big about it. Intel still goes by a bus and the bus sets hte frequency. Buying pc2 800 cas 4 and pc2 800 cas 5 you may see 1% difference if not less. Same holds true for pc2 667.

Also, if you dont overclock, buying DDr2 800 or ddr2 667 at almost any cas would be the same as the ram will underclock itself to pc2 533 and assume the tighter timing of 3-3-3-8.

AMD's hypertransport is different, they want hte fastest and tightest timed ram available.

 

[weilin]

here was my full explaination:

Edit: Taken from "Debate: Is Core 2 Duo a Paper Launch"

Ok all things (including flames) aside (to clear up the situtation and stop confusing the people here), Conroe's 1066mhz Bus Speed is really a 266mhz front side bus (fsb) quad pumped (266x4=1066).

The minimum "requirement" ram wise for that is ddr2 533mhz PC2 4200. How this works is that ddr2 533mhz ram really operates at a frequency of 266mhz. However, because its double data rate, it sends data on the rising and falling edge of each clock thus giving it the effective operation frequency of 266x2 or 533mhz.

The next step to achieveing a effective 1066mhz is the use of Dual Channel memory architecture. Dual channel operation utilize 2 64 bit data channels (opposed to the single channel operation with 1 64 bit data channel) which essentially doubles bandwidth once more by doubling the amount of data sent per clock resulting in a effective frequency of 533x2 or 1066mhz which is what Conroe (Core 2 Duo) cpus require.

The problem stems from people accidently confusing double data rate (DDR) with dual channel operation.

As for all those Enthusiasts, buying the bare minimum is completely out of the question so they go after faster memory models such as ddr2 667 or ddr2 800 or ddr 1066 or higher. Their primarly concern is extreme overclocking but thats a totally different issue.

I hope this helped, also those who want sources please ask, im feelin really lazy typing all this and dont feel like lookin the sources up now.

**Edit** This information only applies to all Intel's processors supporting DDR Ram technology (ok and AMD Athlon XP series and older). Current Generation of AMD procesors utilize something call Hypertransport which doesn't follow everything that i have said above.

 

[second_derivative]

Dual channel would take ddr2 533mhz ram and double it once more resulting in a effective frequency of 533x2 or1066mhz which is what Conroe (Core 2 Duo) cpus require.

but that was my point, this is not true. dual channel doesn't double your frequency, it doubles the bus width, so you're essentially transferring more data per cycle, however you are not transfering more often.

The problem stems from people accidently confusing double data rate (DDR) with dual channel operation.

and you did.

 

[FITCamaro]

Today pairs of DDR SDRAM are run in whats called dual Channel. Ram is usually advertised with its single channel speeds (DDR2 533 is 533mhz by itself). If you put 2 sticks of that ram together in a dual channel capable board you will get Dual Channel Operation or 533x2 or 1066.

i disagree, to my understanding it works like this: the processor gets a "system" clock 266MHz (the FSB is quad pumped making the effective bandwidth 266Mhz*4=1066MHz),

your DDR SDRAM receives this same "system" clock (assuming 1:1 divider), but due to the Double Data Rate (transfer on rising and falling edges of the clock) the effective clock is 2*266MHz=533MHz.

Finally a guy whos right.

System bus runs at 266MHz, not 1066MHz, and is then quad pumped. Memory clock is the same * 2 because of DDR. Running faster RAM than DDR2-533 creates an asynchronous scenario unless you overclock the system bus. Not to say it won't potentially be faster though. Getting high quality, faster memory lets you overclock more and keep a synchronous environment plus have tighter timings.

 

[orionman]

Ok the e6600 has a 1066 Bus. the ram "required" for it is really ddr2 533 as ddr2 533 in dual channel operation runs at 1066 mhz.

YOU absolutely have no idea what you are talking about, don't you?

 

[FITCamaro]

Ok the e6600 has a 1066 Bus. the ram "required" for it is really ddr2 533 as ddr2 533 in dual channel operation runs at 1066 mhz.

YOU absolutely have no idea what you are talking about, don't you?

Well his reason is completely wrong but he is still right.

 

[orionman]

Ok the e6600 has a 1066 Bus. the ram "required" for it is really ddr2 533 as ddr2 533 in dual channel operation runs at 1066 mhz.

YOU absolutely have no idea what you are talking about, don't you?

Well his reason is completely wrong but he is still right.


hummm no??
there no way a ddr2 533 = 2x533 = 1066

 

[illinikevin]

Check out this review. They show conroe performance vs. memory speed. Basically the higher bus only gives you a few percent increase. I'd say get the fastest ram you can afford but last time I checked the 1066 ram cost twice as much as the 800.

http://www.madshrimps.be/?action=getarticle&articID=472

 

[Acadien42]

This is slightly offtopic but I'm wondering where RAMBUS fits in to these comparisons?

I used to own a P4 3.0 Ghgz CPU with a P4T-533-C motherboard and 1.5 Gigs 1066 RDRAM.

I guess my question is how would that system have compared to today's systems with 1066 ram???

thanks!

 

[weilin]

When i explained it, i included the word "effective" which means while it doesnt actually double it, the resulting operation would be like doubling it.

This was typed up leaving a bit of details out to keep the explaination simple. Thats all.

**Edit** I editied the post before to include the whole explaination so this stupid argument can stop now.

 

[nobly]

i disagree, to my understanding it works like this: the processor gets a "system" clock 266MHz (the FSB is quad pumped making the effective bandwidth 266Mhz*4=1066MHz),

your DDR SDRAM receives this same "system" clock (assuming 1:1 divider), but due to the Double Data Rate (transfer on rising and falling edges of the clock) the effective clock is 2*266MHz=533MHz.

a single channel of ram has a 64-bit interface to the FSB so the data transfer rate is 533Mhz * 64-bit data bus * 1byte/8bits = 4200 MB/s thus the PC2-4200 rating.

when you use a pair of modules and run dual-channel configuration you effectively increase the width of the databus to 128 bits, thus doubling your data transfer rate. i'm emphasizing that your effective clock has not changed, though your performance improved greatly.

Very good explanation. This is correct.

also, a question for the more knowledgeable: what's more important the CL timings or RAM bandwidth, for example comparing DDR2-667 CL4 to DDR2-800 CL5?

I'm not claiming to be more knowledgeable but i'll offer a theory:
The difference between CL4 and CL5 is 1 clock cycle, right?
But DDR2-667 has a clock rate of about 1.5ns, whereas DDR2-800 has a clock rate of about 1.25ns. So thus, DDR2-667 CL4 has a total latency of 1.5ns*4 = 6ns, and DDR2-800 CL5 has a total latency of 1.25*5 = 6.25ns.
So which is better? Well, the DDR2-667 CL4 has a better latency rate, but a lower rated speed, which may constrain overclocking. But in all honesty, .25ns... you'll probably never ever even notice it.
Also I think the answer to your question would need to factor in what CPU you are using.

Some memory articles:
http://www.tomshardware.com/2004/01/19/ups_and_downs/index.html
http://www.tomshardware.com/2006/03/31/tight_timings_vs_high_clock_frequencies/
Anandtech showing only marginal increases when going 667->800
http://www.anandtech.com/memory/showdoc.aspx?i=2800&p=7

 

[weilin]

The goal before this scientific debate came up was the keep the post simple and so i left a bit of details out thats all. If i just said 533 is enough and left it as that i would have confused him some more. So i left it as 533 in dual channel and said it was 1066 to match the bus speed of Conroe just to keep it simple (even if it was a tad bit wrong). I have already said that SEcond_Derivative is right in my reply to him, but i was never intending to make a simple answer to his question become a argument over the exact operation procedure of ram.

 

[rwpritchett]

i disagree, to my understanding it works like this: the processor gets a "system" clock 266MHz (the FSB is quad pumped making the effective bandwidth 266Mhz*4=1066MHz),

your DDR SDRAM receives this same "system" clock (assuming 1:1 divider), but due to the Double Data Rate (transfer on rising and falling edges of the clock) the effective clock is 2*266MHz=533MHz.

a single channel of ram has a 64-bit interface to the FSB so the data transfer rate is 533Mhz * 64-bit data bus * 1byte/8bits = 4200 MB/s thus the PC2-4200 rating.

I noticed that newegg sells DDR2-533 RAM as PC4200 and PC4300 rated as well as DDR2-667 RAM as PC5300 and PC5400 rated. Why do some RAM sticks have higher transfer rates at the same bus frequency and are there any issues/advantages in using the PC4300 or PC5400 RAM? Someone please explain more on how the rating is calculated.

 

[nobly]

A guess:

I think PC4300 and PC5400 are just slightly overclocked versions of DDR2-533 and DDR2-667, respectively.

Using the equation second_derivative provided, 4300MB/s / 8bytes = 537.5Mhz. And 5400MB/s / 8bytes = 675Mhz.
As you can see on newegg, some PC5400's are also designated DDR2-675, which would fit.

I think there's no formal JEDEC standard for PC4300 and PC5400, hence why some are labelled DDR2-667 and others are rated DDR2-675.

 

[darkstar782]

The CPU has a 266MHz clock, a 64bit wide bus, and performs 4 transfers per clock cycle (hence 1066).

You are right a 1:1 divider is nice, in this case 2 DDR2-533 DIMMs in Dual Channel means a 266MHz clock, a 128bit wide bus, and 2 transfers per second, hence 533.

This is why Dual Channel was always pretty pointless on the Athlon XPs imho, as if the CPU only has 3.2gb/s of FSB bandwidth then whats the point in 6.4gb/s of memory bandwidth. The only use is for AGP arpetures etc.