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Help overclocking memory

post #1 of 31
10/28/08 at 10:33am
Thread Starter 
I have corsair DDR2 xms2 DHX 800mhz 2x2gb with fins for cooling. Default voltage is 1.8. Cas is 555-18. My board is p5q-em and cpu is E8400. CPU FSB is 1333. Is it true I should match my memory timings with FSB? How do I do this? Eventually I'll be gaming on this, but not for a while. Will I gain other system performance by speeding mhz to 1066 or increasing cas to 4-4-4-18? I presume I'd have to increase voltage to achieve either of these results. If this memory is not ideal for overclocking my sysem let me know what I should buy, and I'll put this memory in my Dell which prefers native 1.8 volts but has no overclocking ability. Thanks again AVS'ers
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post #2 of 31
10/28/08 at 11:00am
You can increase the memory divider, which is now probably 2:3, to increase the frequency while keeping FSB constant; increase the FSB, e.g., try 8*375 or 7*429 instead of your current 9*333, while keeping memory 1:1; and/or lower the performance level setting in the P5Q's BIOS.

Yes, you will likely need higher voltage if you're going beyond the memory's rated speed. Use as little as possible, don't go above 2.1v, and be warned that the P5Qs tend to overvolt memory already. Don't overvolt just for the sake of overvolting or to "be on the safe side."

Do NOT lower timings as it will not affect performance and could easily destabilize your system.

Personally, I recommend that you leave the memory alone. The performance difference from faster memory is anywhere from non-existent to negligible and it is quite easy to mess up your system with unstable memory. If you want a faster system, overclock the CPU/FSB while keeping memory within its rated limits.
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post #3 of 31
10/28/08 at 12:01pm
In Core 2 Duo systems, memory is connected to the CPU (E8400 in your case) via the FSB (front side bus; and the memory bus) whose maximal theoretical bandwidth is

- 1333MT/s x 64bit/8bit = 10.666GB/s.

(Pentium and Core 2's FSB is 64-bit wide.) That only equals the bandwidth of dual-channel DDR2-667 or PC2-5300:

- 667MT/s x 64bit/8bit x 2 (dual channel) = 10.666GB/s.

(DIMMs have a 64-bit data path.) Therefore there is no big performance growth if you use memory faster than DDR2-667 (read this article for more details).

At default settings, your memory runs at 400MHz with multiplier 1.2 = 5:6. You could overclock memory by raising multiplier, say to DDR2-1111 (multiplier 1.66 = 3:5; choose FSB 800 Strap in BIOS) and voltage (read this article). But then FSB 333MHz would be the bottleneck. The correct way to improve memory performance is raise FSB with a lower multiplier, say, 1 or 1.2 or 1.25. (Of course CPU is also overclocked.) But overclocking memory is useful only for applications that are sensitive to the memory subsystem (e.g. games). A typical moderate oc case is:

- FSB: 400MHz
- CPU: 3.6GHz
- Memory: 400MHz or 480MHz (DDR2-800 or DDR2-960; choose FSB 1333 Strap) with 5-5-5-12, 2.1V
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post #4 of 31
10/28/08 at 12:08pm
To indirectly address your question: Why are you trying to overclock memory in a HTPC? Stability should be king in this type of application and the performance gains to be had by memory overclocking are especially slim.
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post #5 of 31
10/28/08 at 12:23pm
Thread Starter 
I do plan on gaming with this at some point although it will be mostly a HTPC. I'm hoping I can keep separate hardware profile settings to easily switch between depending on if I'm gaming or watching movies. I'd like to know if this xms2 ram is good for gaming or should I put this in my Dell and look for something better? I'm looking at gettng a zalman heatsink for my cpu so my cpu should be able to overcolock nicely from what I undrestand.
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post #6 of 31
10/28/08 at 12:28pm
Yep, good for gaming.
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post #7 of 31
10/28/08 at 12:47pm
Thread Starter 
So to maximize gaming performance I raise FSB with a lower multiplier, say, 1 or 1.2 or 1.25. (Of course CPU is also overclocked)? And don't bother lowering CAS to 4-4-4-18 or mhz?
However, if there is much better more overclockable Ram for gaming in my setup, please let me know what it is, and I'll just put these in my dell.
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post #8 of 31
10/28/08 at 1:26pm
Quote:
Originally Posted by leiff View Post

So to maximize gaming performance I raise FSB with a lower multiplier, say, 1 or 1.2 or 1.25. (Of course CPU is also overclocked)? And don't bother lowering CAS to 4-4-4-18 or mhz?
However, if there is much better more overclockable Ram for gaming in my setup, please let me know what it is, and I'll just put these in my dell.

To maximize gaming performance, get a better video card. Seriously, that is by far the most important factor. You can overclock your video card for even better performance.

The next factor is CPU performance. You can overclock your CPU -- either by increasing the frequency, using a higher FSB, or both -- but based on your questions it seems as though this might be your first time. So be sure to read some basic overclocking information before messing with your system. Still, no matter what you do CPU performance is not going to affect your gaming performance as much as the video card will.

Memory performance variance is negligible at best; compared to video card and CPU it is insignificant. Do not waste money on more memory, do not try overclocking memory as a first step, and do not lower your memory timings as this will not help you accomplish your goal. If you want a faster system, buy MORE memory, not faster memory.
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post #9 of 31
10/28/08 at 2:05pm
Quote:
Originally Posted by leiff View Post

So to maximize gaming performance I raise FSB with a lower multiplier, say, 1 or 1.2 or 1.25. (Of course CPU is also overclocked)? And don't bother lowering CAS to 4-4-4-18 or mhz?
However, if there is much better more overclockable Ram for gaming in my setup, please let me know what it is, and I'll just put these in my dell.

In general higher memory clock with lower timings gives better frame rate than lower clock with higher timings. But performance difference in gaming between DDR2-800 and DDR2-1000 (at the same FSB) is often very little (say, only a couple of frame rates) (although you may see more difference if you run memory benchmarks).

If you have a plan to buy new memory modules anyway, G.SKILL F2-8000CL5D-4GBPQ (DDR2-1000, 2 x 2GB; $68) or G.SKILL F2-8500CL5D-4GBPK (DDR2-1066, 2 x 2GB; $80) is a good choice (good performance, but not terribly expensive). Otherwise, stay with your current memory.
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post #10 of 31
10/28/08 at 2:25pm
Quote:
Originally Posted by renethx View Post

In general higher memory clock with lower timings gives better frame rate than lower clock with higher timings.

I have a P5Q board (Deluxe version), and lower timings gave NO performance benefit whatsoever on a synthetic memory benchmark. Same result on a prior P965 board. Don't lower those timings.

The factors that will significantly affect memory performance are: (1) FSB, (2) performance level (a new tweak on P5Q boards), and (3) memory clock (FSB * divider).
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post #11 of 31
10/28/08 at 2:30pm
You need to understand that memory manufacturers, cpu manufacturrs and graphic chip makers make all of their chips to run at the maxiumum speed they can. Then after testing them sell them at the speed at which they were satisfactorily tested. So by overclocking you are just asking for trouble since you are running the chip at a speed that it did not pass factory testiing.
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post #12 of 31
10/28/08 at 2:41pm
Thread Starter 
I do need more memory anyway. Either cheap 1.8 volt for my dell, or give this memory to my dell since it's already 1.8v, and get better memory for this rig. If getting for this rig, are there any specific specs I should be looking for to match well with P5Q-em/ E8400? Am I getting better performance for the f2 ram which is $12 more considering I can overclock either you link to? Of coarse I plan on getting graphics card and overclocking cpu as well later on.
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post #13 of 31
10/28/08 at 2:42pm
Quote:
Originally Posted by nm88 View Post

I have a P5Q board (Deluxe version), and lower timings gave NO performance benefit whatsoever on a synthetic memory benchmark. Same result on a prior P965 board. Don't lower those timings.

Sorry I mean 'looser timings'. What I was trying to say is timings does not matter.
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post #14 of 31
10/28/08 at 2:47pm
Thread Starter 
So what's important in memory is: FSB, and FSB divider. Not 800mhz vs. 1066 mhz, or 4 vs 5 vs 6 cas timings. OK, but how do I know when selecting memory , what will have best FSB/divider timings?
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post #15 of 31
10/28/08 at 3:10pm
I have used P5Q-EM with G.SKILL F2-8000CL5D-4GBPQ and they work fine together.

The available memory multipliers with P45/G45 chipset are:

FSB 800 Strap

- DDR2-667 = 3:5 = 1.66
- DDR2-800 = 1:2 = 2

FSB 1066 Strap

- DDR2-667 = 4:5 = 1.25
- DDR2-800 = 2:3 = 1.5
- DDR2-1066 = 1:2 = 2

FSB 1333 Strap

- DDR2-667 = 1:1 = 1
- DDR2-800 = 5:6 = 1.2

FSB 1600 Strap

- DDR2-800 = 1:1 = 1

For example, if you want to get CPU to run at 3.6GHz, you will set FSB = 400MHz. Then you can set memory multiplier to any value you like as long as memory runs within the specs (500MHz = DDR2-1000 in the case of F2-8000CL5D-4GBPQ): 1, 1.2, 1.25 (choose the proper strap before that). The next value is 1.5, with which you memory would run at 400MHz x 1.5 = 600MHz = DDR2-1200, that may cause instability or even crash of the system. If you choose DDR2-1066, you will have more headroom for FSB at mem multiplier 1.25 (FSB = 426.4MHz assuming mb/CPU runs fine at that speed). (But you can always lower it to 1.2 with DDR2-1000...)

So my suggestion is choose either one depending on your budget (although you need to check the compatibiltiy of F2-8500CL5D-4GBPK with P5Q-EM).

And leave the timings and voltage at default (5-5-5-15 and 2.1 V in the case of F2-8000CL5D-4GBPQ). Changing the timings is not worth the effort. If you raise voltage, memory could run at higher clock, of course ...
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post #16 of 31
10/28/08 at 5:10pm
Even though I am not an expert, I feel I should chime in because syncing my FSB/memory turned out to be the solution to my playback stutering problems. (I apologize to the techies for these posts...the skillset of my audiences were unclear

My post

Another post

It is interesting to note that I decreased my memory speed in order to sync it to the FSB. (Although I did overclock my FSB to 1333.)

It sounds like we have similar setups (just in terms of speed,) here's mine:
680i LT MOBO/Intel Q6600 Quad processor...overclocked to 3.0Ghz (Simple overclock: raised FSB to 333 (rated FSB 1333) x9 (multiplier) = 3000MHz)

4 GB 800MHZ dual-channel memory -> decreased from 400Mhz (800MHz dual-channel)->333Mhz (still 667 dualch) (4:4:4:15:2T)

This gives me a "FSB : DRAM ratio" of 1:1...

Without going into detail, it is confusing at first because of all the different multipliers. (E.g. 800Mhz "dual-channel" sounds faster than a resident speed of 400Mhz, so they market the former.) But getting rid of all of these terms...333 FSB : 333 MHz memory = 1:1 ratio.

I have a fast computer. I built it myself. I am proud of it...But to this day I am absolutely astonished how much smoother BluRay/HD-DVD playback became once I synced up my memory.

With your FSB already at 1333, you are most of the way there. Syncing should be a simple matter of going into the bios and setting the memory to 333 from 400. Yes, normally you have to increase voltages when raising memory timings, but it obviously does not apply here. I hope you have as much of a performance increase (particularly in regard to smooth playback) as I have... (Oh and feel free to PM me if I can help further...))
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post #17 of 31
10/28/08 at 6:28pm
Thread Starter 
I want to use my rig as a sometime game machine. So I was hoping to overclock cpu to 3.6GHz for gaming. But since It will mainly be used for movies, is there advantage for taking cpu back to stock 3 GHz when watching movies? Will it run less hot/loud and conserve power? If this is the case, I was hoping to somehow save hardware profiles to easily switch on and off overclocking. Can this be done? Because if I understand correctly, both cpu and memory settings have to be changed together to stay in sync, and this would make manual adjustments more tedious.
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post #18 of 31
10/28/08 at 8:50pm
Quote:
Originally Posted by leiff View Post

So what's important in memory is: FSB, and FSB divider. Not 800mhz vs. 1066 mhz, or 4 vs 5 vs 6 cas timings. OK, but how do I know when selecting memory , what will have best FSB/divider timings?

Memory speed = FSB * divider/ratio.

So if your divider is 1:1, your memory speed is equal to FSB (doubled to account for DDR). If your divider is 2:3, then your memory speed is 1.5 times your FSB, meaning 800 DDR for your default 333 FSB.

The P5Q's BIOS doesn't list dividers, but rather concrete memory frequencies. So you simply pick from a list of possible choices.
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post #19 of 31
10/28/08 at 8:51pm
Quote:
Originally Posted by leiff View Post

Am I getting better performance for the f2 ram which is $12 more considering I can overclock either you link to?

Get this Corsair set. It's only $45 after MIR with free shipping, for 4 Gb DDR2 800 (2x2 Gb). I have no idea why you'd want to pay 50% more for memory from G Skill, a lesser brand.
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post #20 of 31
10/28/08 at 8:55pm
Quote:
Originally Posted by leiff View Post

I want to use my rig as a sometime game machine. So I was hoping to overclock cpu to 3.6GHz for gaming. But since It will mainly be used for movies, is there advantage for taking cpu back to stock 3 GHz when watching movies?

No. Overclock, test stability, then leave it there.
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post #21 of 31
10/29/08 at 1:15am
Quote:
Originally Posted by myurkus View Post

Even though I am not an expert, I feel I should chime in because syncing my FSB/memory turned out to be the solution to my playback stutering problems. (I apologize to the techies for these posts...the skillset of my audiences were unclear

My post

Another post

It is interesting to note that I decreased my memory speed in order to sync it to the FSB. (Although I did overclock my FSB to 1333.)

It sounds like we have similar setups (just in terms of speed,) here's mine:
680i LT MOBO/Intel Q6600 Quad processor...overclocked to 3.0Ghz (Simple overclock: raised FSB to 333 (rated FSB 1333) x9 (multiplier) = 3000MHz)

4 GB 800MHZ dual-channel memory -> decreased from 400Mhz (800MHz dual-channel)->333Mhz (still 667 dualch) (4:4:4:15:2T)

This gives me a "FSB : DRAM ratio" of 1:1...

Without going into detail, it is confusing at first because of all the different multipliers. (E.g. 800Mhz "dual-channel" sounds faster than a resident speed of 400Mhz, so they market the former.) But getting rid of all of these terms...333 FSB : 333 MHz memory = 1:1 ratio.

I have a fast computer. I built it myself. I am proud of it...But to this day I am absolutely astonished how much smoother BluRay/HD-DVD playback became once I synced up my memory.

With your FSB already at 1333, you are most of the way there. Syncing should be a simple matter of going into the bios and setting the memory to 333 from 400. Yes, normally you have to increase voltages when raising memory timings, but it obviously does not apply here. I hope you have as much of a performance increase (particularly in regard to smooth playback) as I have... (Oh and feel free to PM me if I can help further...))

Perhaps your problem is specific to the nForce 680i (LT) SLI chipset. As the memory controller is totally different from Intel's, it's hard to apply the same argument to P45/G45. In fact nobody has reported video playback problems with memory running at a multiplier other than 1.
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post #22 of 31
10/29/08 at 1:28am
Quote:
Originally Posted by leiff View Post

I want to use my rig as a sometime game machine. So I was hoping to overclock cpu to 3.6GHz for gaming. But since It will mainly be used for movies, is there advantage for taking cpu back to stock 3 GHz when watching movies? Will it run less hot/loud and conserve power? If this is the case, I was hoping to somehow save hardware profiles to easily switch on and off overclocking. Can this be done? Because if I understand correctly, both cpu and memory settings have to be changed together to stay in sync, and this would make manual adjustments more tedious.

If you turn on Enhanced Intel Speedstep Technology (EIST) or C1E in BIOS, your CPU automatically slows down to 400MHz x 6 = 2.4GHz and voltage 1.15V at idle (including movie playback [unless you change CPU voltage]). So basically you don't have to change settings in games and video playback. The difference of power consumption between 2.0GHz (default at idle) and 2.4GHz (oc at idle) is very small (a few watts).

Of course you can use ASUS O.C. Profile in BIOS to save each BIOS settings for games and HTPC respectively as a profile and load a proper profile at start-up.
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post #23 of 31
10/29/08 at 12:13pm
best advice.... DON'T !!

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post #24 of 31
10/29/08 at 12:57pm
Thread Starter 
mm88 says don't bother saving profiles in bios for gaming/movies; changing CPU from 3.6 to to mid 2.4 GHz range. I won't bother unless someone thinks it's a good idea. Once I get a video card, I'm hoping there is a easy way to switch between card GPU for games; and onboard GPU for movies without removing card. This is advisable and will save electricity and keep my system cooler when not gaming right?
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post #25 of 31
10/29/08 at 1:08pm
Toms Hardware has done testing of DDR2 speeds and even if dual channel is truly faster than single channel anymore and guess what? Memory was found to have very little impact on modern systems. Even when changing to a single channel, a Core2Duo or X2 was still nearly as fast if not so close it was statistically irrelevant.

I seriously recommend that unless you are a crazy speed demon that brags about every last % of performance, you leave your memory clock and timings alone. Concentrate on getting a better vid card as has been pointed out above. The number one bottleneck on any modern dual core system is the video card and not the CPU or RAM.

http://www.tomshardware.com/reviews/...G,1705-11.html

Given that there is a MASSIVE amount more bandwidth from going dual channel than just bumping the clock speed a bit, overclocking your RAM is generally the most futile thing you can do.

Look at the following:

http://www.tomshardware.com/reviews/...y,2013-14.html

Even though it is comparing DDR3 types, it shows that the jump from 1333 to 1600 provides for very little performance gain in games. Certainly not enough to justify the price or to justify the risk of overclocking your RAM.

Some more info to consider...

http://www.tomshardware.com/reviews/...r,1627-12.html

http://www.tomshardware.com/reviews/...00,1535-5.html

There is simply not enough benefit to outweigh the costs or the instability risks.
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post #26 of 31
10/29/08 at 1:14pm
Thread Starter 
It's still advisable to sync clock timings FSB- between cpu and memory; I get the impression though.
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post #27 of 31
10/29/08 at 1:20pm
Hmm.. I find it odd that most of you are recommending you don't lower CAS timings. Most gaming benchmarks I have seen show that CAS timings have a bigger effect on in game performance than the memory's actual clock speed. I can dig up a link later on if need be.

With that said though, the difference is still small either way. If you have DDR800 @ 5-5-5-12 your not going to see a large performance increase in games by overclocking. Maybe a frame or 2. You may want to relax the timings and increase the clock speed to get a 1:1 ratio, just so you don't run into a bandwith bottleneck when doing other things like decoding/encoding, but it really won't effect games much.
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post #28 of 31
10/29/08 at 3:00pm
Quote:
Originally Posted by Tree Dude View Post

Hmm.. I find it odd that most of you are recommending you don't lower CAS timings. Most gaming benchmarks I have seen show that CAS timings have a bigger effect on in game performance than the memory's actual clock speed.

It's very system-dependent. On some AMD boards I've used, it made a small difference. On the P5Q (P45 board) and a P965 board I've tested, it made no difference.

However, on all boards, tight timings can very easily destabilize the system, so it's something you want to be very careful with.
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post #29 of 31
10/29/08 at 3:25pm
Quote:
Originally Posted by leiff View Post

Once I get a video card, I'm hoping there is a easy way to switch between card GPU for games; and onboard GPU for movies without removing card. This is advisable and will save electricity and keep my system cooler when not gaming right?

This is exactly the feature (almost) every gamer wants. Unfortunately, only one chipset family supports this feature right now: GeForce 8200/8300 and nForce 750a/780a SLI (for AMD). The feature is called Hybrid Power and works with GeForce 9800 GT and higher. But NVIDIA made a big blunder of removing it from the latest GeForce 9300/9400 chipset for Intel.
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post #30 of 31
10/29/08 at 6:05pm
Quote:
Originally Posted by leiff View Post

Once I get a video card, I'm hoping there is a easy way to switch between card GPU for games; and onboard GPU for movies without removing card. This is advisable and will save electricity and keep my system cooler when not gaming right?

Your Geforce core and memory will automatically downclock (a lot) when you're not stressing them, saving you energy when you're not gaming. (Unless your point is that you need the features of your on-board video.)

If you want save energy, the best possible thing you can do is set your system to go to sleep when not in use. Massive savings, for the typical user.
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