Overclocking DDR3

[PCJake]

I'll probably be making the switch from my GA-EP35-DS3L board to a 790i FTW, and I'll need to be getting some DDR3 RAM. My current overclock on my Q6600 is 3.33GHz (370x9).

I had been looking at 4GB of G.Skill DDR3 1333, but would this give me trouble when I'm overclocking? 1333/4=333.25, and I want to get that FSB to at least 370, where it is now. Would a need to go with DDR3 1600 for sure (big price jump), or am I not looking at it correctly?

Thanks!

 

[BTRY B 529th FA BN]

DDR3 1600 is where you want to be.

 

[PCJake]

I should probably be posting this in the memory section, but how does this set look as a solution? It's fairly cheap, but I like G.skill, I just don't want to miss something important.

 

[Denithor]

You don't divide memory speed by four you divide it by two. DDR3-1333 will handle up to an fsb of 666 at stock speed on a 1:1 multiplier. Which is why there's very little need to run DDR3 at this point (DDR2 provides more than adequate bandwidth and speed).

 

[PCJake]

Originally posted by: Denithor
You don't divide memory speed by four you divide it by two. DDR3-1333 will handle up to an fsb of 666 at stock speed on a 1:1 multiplier. Which is why there's very little need to run DDR3 at this point (DDR2 provides more than adequate bandwidth and speed).

I don't know who to believe at this point. I've got two experienced members telling me opposite things. All the evidence I find in other threads and forums leads me to believe it's divided by four...

 

[chess9]

http://forums.anandtech.com/me...=2190613&enterthread=y
There's an example for DDR2 there.

-Robert

 

[Markfw]

I PM'ed N7, the memory moderator. If he replies, trust him, he is the memory god.

I am pretty sure its / 2. PC 800 DDR2 1000 runs at 500 mhz, I know that.

 

[Idontcare]

DDR3 is 4x the FSB's base clock. It runs at exactly the FSB quad-pumped speed when set to 1:1.

A 1333 MHz FSB (333MHz base clock, quad pumped to 1333MHz) will operate DDR3 at 1333 MHz (4x333) when the bios is set to "synch" mode or also called "1:1" mode.

For DDR2 it is 2x the FSB's base clock when the BIOS is set to operate in synch mode or 1:1 mode.

A 1333MHz FSB will operate DDR2 at 667MHz (2x333) when the BIOS is set to sync or 1:1 mode.

http://en.wikipedia.org/wiki/Memory_divider

 

[PCJake]

Originally posted by: Markfw900
I PM'ed N7, the memory moderator. If he replies, trust him, he is the memory god.

I am pretty sure its / 2. PC 800 DDR2 1000 runs at 500 mhz, I know that.

Awesome, I'll be checking back often. I'm finally starting to find sources stating that DDR3 1333 will handle up to a 667 fsb. Needless to say, that would be plenty.

DDR3 is 4x the FSB's base clock. It runs at exactly the FSB quad-pumped speed when set to 1:1. A 1333 MHz FSB (333MHz base clock, quad pumped to 1333MHz) will operate DDR3 at 1333 MHz (4x333) when the bios is set to "synch" mode or also called "1:1" mode.

Yes, but I need to know if I can run it above 1333. If I use a 400 fsb, then will it try to run at 1600 speeds? That's much higher than it's rated.

 

[daw123]

Originally posted by: graysky
3. Memory[/b]
You will need memory that can keep up with your overclocked system. Again, I?m not going to keep a list. You?ll see RAM listed with timings and speeds that I?ll decode for you using the following examples:

DDR2-800 (PC2-6400) 4-4-4-12
DDR2-1066 (PC2-8500) 5-5-5-15

? The first part is self-explanatory (DDR2 memory).
? The number after it is the data transfer rate. Simply divide it by 2 to get the maximum FSB speed for which the module is rated. Example: 800/2 = 400 MHz. Therefore, DDR2-800 can work on systems with a FSB of up to 400 MHz (anything more and you?re lucky).
? The PC2-XXXX is designation denoting theoretical bandwidth in MB/s. Some memory manufactures use this instead of the DDR2-xxx designation. You can calculate it for any FSB you want by simply taking the FSB and multiplying by 16 (rounded in some cases). Example using a 400 MHz FSB: 400x16=6400. So you?d need at least PC2-6400 to run on a FSB of 400 MHz.

The numbers after that are the main timings (clock cycles). In general, the lower these numbers are, the faster the memory. For more on memory timings, see this page.

DDR3-1333 (PC3-10666) 9-9-9-24
DDR3-1600 (PC3-12800) 7-7-7-20

? The first part is self-explanatory (DDR3 memory).
? The number after it is the data transfer rate. Simply divide it by 4 to get the maximum FSB speed for which the module is rated. Example: 1600/4 = 400 MHz. Therefore, DDR3-1600 can work on systems with a FSB of up to 400 MHz (anything more and you?re lucky).
? The PC3-XXXXX is designation denoting theoretical bandwidth in MB/s. Some memory manufactures use this instead of the DDR3-xxxx designation. You can calculate it for any FSB you want by simply taking the FSB and multiplying by 32 (rounded in some cases). Example using a 400 MHz FSB: 400x32=12800. So you?d need at least PC3-12800 to run on FSB of 400 MHz.

The above quote is from Graysky's overclocking guide (the sticky at the top of this category).

You divide the transfer rate by 2 for DDR2 and divide by 4 for DDR3.

Examples
DDR2: 800MHz (or PC-6400) = 400MHz FSB
DDR3: 1600MHz (or PC-12800) = 400MHz FSB

POST EDIT: I stand corrected by n7. You learn something new every day.

 

[n7]

You don't require anything more than 1:1, which is DDR3-667.

Obviously, you don't buy DDR3 to run at DDR2 speeds, which is why most of the time, people run 1:2 or similar ratios, which would mean for that ratio you need DDR3-1333 or higher.

But you don't technically do not have to have higher, as you can choose to run a lower ratio.

We had this same argument before; graysky's guide isn't really correct for DDR3 requirements.

Please see my posts in this thread from before: http://forums.anandtech.com/me...ey=y&keyword1=ddr3-667

 

[BTRY B 529th FA BN]

Originally posted by: PCJake
I should probably be posting this in the memory section, but how does this set look as a solution? It's fairly cheap, but I like G.skill, I just don't want to miss something important.

Those aren't too bad, but timings do make a difference. For example, I ran my SuperTalent DDR3 1600 at 454fsb at 1:1 which equaled 908Mhz at 5.5.5.15 and it was noticeably faster than 7.7.7.21 ; I haven't ran my DDR3 machine in such a while I couldn't tell you and be for sure about the way it operates. I had a Q9300 with a 7.5 multi and at 454 FSB (908Mhz operational speed) I think it ran 3.4Ghz but at 1:1 If I ran it 1:2 which it's suppose to be ran at 400fsb would be my limit. So, 7.5x400 gave me 3Ghz on the Q9300 at 1:2 DDR3 1600Mhz

 

[PCJake]

Originally posted by: n7
You don't require anything more than 1:1, which is DDR3-667.

Obviously, you don't buy DDR3 to run at DDR2 speeds, which is why most of the time, people run 1:2 or similar ratios, which would mean for that ratio you need DDR3-1333 or higher.

But you don't technically do not have to have higher, as you can choose to run a lower ratio.

We had this same argument before; graysky's guide isn't really correct for DDR3 requirements.

Please see my posts in this thread from before: http://forums.anandtech.com/me...ey=y&keyword1=ddr3-667

Excellent, thank you, the link made it clear.

Would I see a significant performance gain if I were to run DDR3 1600 with a 1:2 divider compared to DDR3 1333 with a 3:5 divider (both running right up to rated speeds)?

Also, I was able to run my DDR2 800 at around 950 MHz. Will the overclocking potential increase proportionally (DDR3 1333 at 1633 MHz: 300 mhz overclock compared to 150)?

 

[PCJake]

Originally posted by: BTRY B 529th FA BN

Originally posted by: PCJake
I should probably be posting this in the memory section, but how does this set look as a solution? It's fairly cheap, but I like G.skill, I just don't want to miss something important.

Those aren't too bad, but timings do make a difference. For example, I ran my SuperTalent DDR3 1600 at 454fsb at 1:1 which equaled 908Mhz at 5.5.5.15 and it was noticeably faster than 7.7.7.21 ; I haven't ran my DDR3 machine in such a while I couldn't tell you and be for sure about the way it operates. I had a Q9300 with a 7.5 multi and at 454 FSB (908Mhz operational speed) I think it ran 3.4Ghz but at 1:1 If I ran it 1:2 which it's suppose to be ran at 400fsb would be my limit. So, 7.5x400 gave me 3Ghz on the Q9300 at 1:2 DDR3 1600Mhz

So the the 3.4 GHz CPU clock with a 1:1 divider and lower timings would trump a 3.0 GHz CPU clock with 1:2 ratio and higher timings? Do you really think the performance jump you noticed was due to the lower timings and not the faster CPU clock?

Now I've got my eyes on this set. It's only DDR3 1333 but the timings are a step lower.

 

[BTRY B 529th FA BN]

Originally posted by: PCJake

Originally posted by: BTRY B 529th FA BN

Originally posted by: PCJake
I should probably be posting this in the memory section, but how does this set look as a solution? It's fairly cheap, but I like G.skill, I just don't want to miss something important.

Those aren't too bad, but timings do make a difference. For example, I ran my SuperTalent DDR3 1600 at 454fsb at 1:1 which equaled 908Mhz at 5.5.5.15 and it was noticeably faster than 7.7.7.21 ; I haven't ran my DDR3 machine in such a while I couldn't tell you and be for sure about the way it operates. I had a Q9300 with a 7.5 multi and at 454 FSB (908Mhz operational speed) I think it ran 3.4Ghz but at 1:1 If I ran it 1:2 which it's suppose to be ran at 400fsb would be my limit. So, 7.5x400 gave me 3Ghz on the Q9300 at 1:2 DDR3 1600Mhz

So the the 3.4 GHz CPU clock with a 1:1 divider and lower timings would trump a 3.0 GHz CPU clock with 1:2 ratio and higher timings? Do you really think the performance jump you noticed was due to the lower timings and not the faster CPU clock?

Now I've got my eyes on this set. It's only DDR3 1333 but the timings are a step lower.

The timings testings were isolated. I wouldn't compare 3.4Ghz to 3Ghz. Comparisons were made at 3Ghz and what I mean is by sense of feel. Not benchmarks. But, I wouldn't come to a conclusion right away. You don't do it like that. Grains of salt, like grains of salt is how I made my judgment.

This is the memory I bought; but from a different vendor. They have a good review here.

To be safe without having to worry about memory overclocking walls DDR3 1600 is your safe bet if you are looking to bring the fsb up to 400 without worries.

 

[PCJake]

Originally posted by: BTRY B 529th FA BN

Originally posted by: PCJake

Originally posted by: BTRY B 529th FA BN

Originally posted by: PCJake
I should probably be posting this in the memory section, but how does this set look as a solution? It's fairly cheap, but I like G.skill, I just don't want to miss something important.

Those aren't too bad, but timings do make a difference. For example, I ran my SuperTalent DDR3 1600 at 454fsb at 1:1 which equaled 908Mhz at 5.5.5.15 and it was noticeably faster than 7.7.7.21 ; I haven't ran my DDR3 machine in such a while I couldn't tell you and be for sure about the way it operates. I had a Q9300 with a 7.5 multi and at 454 FSB (908Mhz operational speed) I think it ran 3.4Ghz but at 1:1 If I ran it 1:2 which it's suppose to be ran at 400fsb would be my limit. So, 7.5x400 gave me 3Ghz on the Q9300 at 1:2 DDR3 1600Mhz

So the the 3.4 GHz CPU clock with a 1:1 divider and lower timings would trump a 3.0 GHz CPU clock with 1:2 ratio and higher timings? Do you really think the performance jump you noticed was due to the lower timings and not the faster CPU clock?

Now I've got my eyes on this set. It's only DDR3 1333 but the timings are a step lower.

The timings testings were isolated. I wouldn't compare 3.4Ghz to 3Ghz. Comparisons were made at 3Ghz and what I mean is by sense of feel. Not benchmarks. But, I wouldn't come to a conclusion right away. You don't do it like that. Grains of salt, like grains of salt is how I made my judgment.

This is the memory I bought; but from a different vendor. They have a good review here.

To be safe without having to worry about memory overclocking walls DDR3 1600 is your safe bet if you are looking to bring the fsb up to 400 without worries.

Unfortunately I can't afford both higher speeds AND lower timings. At any rate, I trust G.Skill and I will likely be able to get that set to outperform my current DDR2 800 set.