# RAM 101 (Intel systems in particular)



## NoAffinity

*RAM 101*

*Basic RAM principles:*

*1) General -* Random access memory relies on an electrical charge, which is constantly refreshed, to hold data. Without power, memory is lost. It does not retain data without power.

*2) Definition -* DDR RAM is Dual Data Rate RAM. If your mobo uses DDR RAM, your BIOS may list RAM frequency (half of RAM's rated DDR speed) or actual DDR speed. The PC equivalent is 8 times the DDR speed or 16 times the actual frequency, e.g. DDR400 runs at 200 MHz and is rated as PC3200 (also DDR2-400 = 400 MHz = PC2-3200). DDR2 works on the same principles as DDR, but it has a 240 pin interface compared to a 184 pin interface for DDR. Unless otherwise states below, info for DDR applies to both DDR and DDR2.

*3) RAM Timings -* Higher numbers (5-5-5-15 and higher are possible) equate to looser timings. Lower number (2-2-2-5 being the typical lowest) equate to tighter timings. Ultimately, a timing is an interval based on clock cycles. If a particular event that coincides with a particular timing is occurring every two clock cycles, then it is running tighter than if it were occurring every 4 clock cycles. The occurrence is effectively happening more quickly (in less clock cycles) with a "tighter" timing.

*4) Dividers -* 1:1 CPU:RAM synchronicity generally offers best performance on Intel systems. Loosening timings to achieve higher FSB will most often offer better performance than tight timings with limited FSB. With this principle in mind when overclocking, achieving the highest CPU FSB even at the expense of very loose RAM timings is the ultimate goal.

*5) Timings vs. Performance -* At any given clock speed, tighter timings will offer better performance than looser timings.

*6) Dividers vs. Performance -* Running RAM faster than the CPU may offer better performance than 1:1. This is particularly true on DDR2 as some DIMMs can run at DDR2-1200 (600 MHz) or faster. If you have found your CPU's maximum frequency and have the headroom to run a divider that will run the RAM faster than the CPU (i.e. your RAM is not yet at its maximum frequency), then go for it. Limiting your CPU overclock to run the RAM faster than the CPU, however, will reduce performance. Again, go for the highest CPU FSB possible first and foremost.

*7) RAM speed vs. Motherboard Specifications -* RAM's rated speed is not its required speed. Even though RAM may be rated to run up to DDR500, for example, it will still run at 400 MHz if that is the corresponding bus speed of the system. Therefore, if your motherboard lists DDR400 or DDR2-800 as the maximum RAM speed, it is very rare that it would not safely run RAM rated at a higher speed.

A few examples: if you have an 800 mhz FSB CPU, and you install DDR500, it will still only be running at DDR400, at stock bus speeds, until you up the mobo's FSB. If you are running a 533 mhz FSB CPU in conjunction with PC3200, the RAM will still be running at 266 mhz in 1:1 at stock bus speeds. The benefit of having faster-rated RAM is to allow for higher overclocking.

*8)* Your mobo will support any speed of RAM above what it is rated for. You can always run faster-rated RAM at slower speeds. The highest official JEDEC DDR RAM speed is PC3200, and all s478 motherboards offer support up to this speed (i.e. w/ an 800 mhz FSB CPU, your highest available divider will be 1:1, which supports DDR400). If you look a little futher into your manufacturer's compatibility list (if they've actually taken the time to test compatibility), you will most likely find that the board does officially support any given higher-rated RAM.

For example, if you can achieve a FSB of 270 with your CPU, then your mobo will support PC4400. If you can achieve a FSB of 240, then your mobo will support DDR500. Again, you can install any faster-rated RAM in your motherboard, but it will only be running at the twice the speed of the system bus.

*9)* If your mobo supports dual channel memory, then take advantage of it. Dual channel memory does not necessarily need to be purchased in a dual channel "kit", but you are best to install two identical matching sticks when running dual channel. If running dual channel with two speeds of RAM, your mobo will only operate in dual channel mode at the speed of the slowest stick. Dual channel memory greatly increases memory throughput (ideally it is supposed to double memory bandwidth, but in reality, this is not true).

*10)* Running RAM slower than the CPU (also referred to as "using a divider") hinders performance.

With these things in mind, as they pertain to overclocking, the following is recommended:

*1)* Find your highest possible CPU overclock, even if this means running a divider.

*2)* Leave timings as loose as possible (3-4-4-8) in 1:1 to establish the highest possible speed that your RAM will achieve.

*3)* If you are using a divider, or you have established that your CPU will not overclock any further, or you have decided that you only want to run your CPU at clock speeds slower than the RAM's max, then start tightening timings to achieve more performance from your RAM.

*4)* If you are looking for maximum performance, and are forced to use a divider to achieve maximum CPU overclock, test your highest 1:1 (assumedly with loose timings) against your highest CPU overclock (with a divider and tightest possible timings). Establish for yourself which offers best performance in your system.

*5)* If you are using a divider, you will greatly improve performance by installing RAM that corresponds with your CPU's overclock (i.e. allow stable 1:1 operation). Along these same lines, if you are in the market for RAM, and want the best performance out of your system, establish your CPU's highest overclock before making your purchase.

Synthetic benchmarks effective in establishing performance and testing stability:

*1)* *Prime 95* (separate CPU and RAM stress tests, along with an overall system stability tester)
*2)* *Memtest86* (tests some CPU, mostly RAM)
*3)* *SiSoftware Sandra* Memory Bandwidth Benchmark Test (establishes memory throughput)
*4)* *3dMark01* (random game tests based on CPU, RAM an video card performance equally)

**For specific examples, see charts at post #12 of this thread*


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## hop1hop2

Good Thread!!!


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## archer_456

excellent breakdown!


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## macg

hmmm.... i think you should specify that memtest also tests for vcore/fsb stability, specifically on tests 1-4. errors in these tests are usually fsb or vcore related, like too high for the former or too low for the latter.

tests 5 and above are geared towards stability of the memory (timings, vdimm).

people often mistake memtest as a "purely" memory related diagnostic. thats why there are many people complaining about pc3500s or pc4000s getting errors on memtest on oc'ed systems, even if they're running below or in spec.

hope this helps


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## macg

oh, and i learned this the hard way =)

searchin the whole net for the memtest functions made me dizzy.

NoAffinity also helped me diagnosing the problem I had


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## NoAffinity

Thanks for clarification, macg, I adjusted it. I've never really used memtest...and I _did_ think it was only a memory tester.


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## macg

Quote:


Originally Posted by *NoAffinity*
Thanks for clarification, macg, I adjusted it. I've never really used memtest...and I _did_ think it was only a memory tester.









i thought so too, for a loooooong time.









i decided to see if there was any truth to the articles i read, mostly on other sites that i had to use a translator on.

i ran my my 2.4a @ 3.6 which was unstable, used memtest and looped tests 1-4. all of them got loads of errors, looped 5 and 8 but got only 2 errors.

ran it again @ 3.4 but with a much lower vcore, still got errors on tests 1-4, nothing on test 5... upped the vcore a notch higher and tests 1-4 were error free... i didnt touch mem timings and vdimm at all..

verified this with a friend from another forum and he got the same results too..

i've read a LOT of posts regarding RMAs of high quality modules mainly because of Memtest errors, and on tests 1-4. guess this should clarify things and help people.


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## macg

oh and btw, great guide you put together!


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## Xavier1421

I vote sticky.


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## NoAffinity

Quote:


Originally Posted by *Xavier1421*
I vote sticky.

ummm....it _is_ sticky.


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## Xavier1421

BWA HA HA HA! Sorry, I musta skipped right over that part...

Boy I feel stupid!


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## NoAffinity

All right guys, I ran some tests, found my initial thought that there was no difference in performance between 4:5 and 1:1 were incorrect, and have charted the results (and amended the guide). As you can see, the difference between 1:1 and 4:5 in anything but bandwidth benchies is negligible. And, of course, higher FSB 1:1 offers the best performance, compared to a lower CPU clock in 4:5. So here it is:


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## Lando95

^^ How about a 166fsb at 4:5 compared to 166fsb at 1:1?


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## NoAffinity

The same principles will apply. Bandwidth will be mildly better in 4:5 than 1:1, but arithmetic and multimedia will not benefit any.


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## prendergaststeve

Quote:


Originally Posted by *NoAffinity*
The same principles will apply. Bandwidth will be mildly better in 4:5 than 1:1, but arithmetic and multimedia will not benefit any.

where is this 4;5 OR 1;1 DONT UNDERSTAND.WHERE DO YOU SET THIS.When I change my fsb all good,the only other things I can change are duh 3:2:1 or 4:2:1 or 5:3:2 or 6:4:2 or spd something like that.Dont laugh I am learning


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## Lostnhell

Quote:


Originally Posted by *prendergaststeve*
where is this 4;5 OR 1;1 DONT UNDERSTAND.WHERE DO YOU SET THIS.When I change my fsb all good,the only other things I can change are duh 3:2:1 or 4:2:1 or 5:3:2 or 6:4:2 or spd something like that.Dont laugh I am learning

You will see the ratio in your BIOS or on a 3rd party app.


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## prendergaststeve

Quote:


Originally Posted by *mfillpot*
You will see the ratio in your BIOS or on a 3rd party app.

I think I can figure this out,if its the last thing I do lol.Thanks for your input.


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## NoAffinity

Do you have an option set set RAM or DRAM speed? If so, then this will dictate the CPU:RAM divider, and won't be displayed as an actual ratio. The ratios that you have available are a ratio for you PCI and AGP buses, divided off of CPU frequency.


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## silentone

yo guys! i'm new on this overclocked.net site. how do you post your computer specs?


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## ThE_GeNeRaL

welcome to the forum!!!!!!!!!!!!

put them in your profile which is listed in your user CP


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## Industrial

Quote:


Originally Posted by *NoAffinity*
All right guys, I ran some tests, found my initial thought that there was no difference in performance between 4:5 and 1:1 were incorrect, and have charted the results (and amended the guide). As you can see, the difference between 1:1 and 4:5 in anything but bandwidth benchies is negligible. And, of course, higher FSB 1:1 offers the best performance, compared to a lower CPU clock in 4:5. So here it is:


Why does that show up 133mhz and 166mhz FSB. That means its a 533mhz (OC to 664) board, right?


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## NoAffinity

Quote:


Originally Posted by *Industrial*
Why does that show up 133mhz and 166mhz FSB. That means its a 533mhz (OC to 664) board, right?

What are you referring to? The system bus speeds tested were 133 mhz FSB and 166 mhz FSB. 133 is the stock system bus speed that a 533 mhz FSB CPU uses. This also produces DDR speeds of 266 mhz. Running 166 mhz FSB put the 2.53 used for testing at 3.154 GHz, and creates DDR speeds of 333 mhz.

Was that your question?


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## fourstar77

I dont get the 1:1 idea, other than I think I understand that it is your FSB compared to the mhz rate of your ram. How do you up the mhz that your ram is running on? Where is that setting?

I have AMD64 proc and an MSI Neo2 K8n Plat w/ OCZ 3700 Gold Rev. 3.

I have been adjusting the FSB, but dont see where you would up the speed of your memory.

Sorry for basic question.

Thanks

Quote:


Originally Posted by *NoAffinity*
ummm....it _is_ sticky.


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## NoAffinity

RAM speed is clocked either synchronously or asynchronously with the CPU when adjusting front side bus. Some mobos list it as FSB, some list it as CPU frequency or CPU clock, but it's all the same: front side bus, which is system bus, which both CPU and RAM run on.


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## fourstar77

So I would want to look for the synchronous or asynchronous option in my bios (and set ty synchronous) to keep my OCZ 3700 Gold Rev. 3 and my MSI K8N Neo2 Plat at the same FSB speed? I think that they are at the same speed, but I will have to verify.

And then I am guessing that is where a divider comes in. If your mobo and proc can handle higher FSB but your ram is capped, you can try to adjust the divider to 5:6 or something to keep Ram at lower/its max speed and to boost the proc speed. I have heard performance is generally better at 1:1 ratio so unless the results are much better it probably is not worth it.

Just let me know if I am on the right track?

Thanks for the help.

Quote:


Originally Posted by *NoAffinity*
RAM speed is clocked either synchronously or asynchronously with the CPU when adjusting front side bus. Some mobos list it as FSB, some list it as CPU frequency or CPU clock, but it's all the same: front side bus, which is system bus, which both CPU and RAM run on.


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## NoAffinity

Yes, you are on the right track. If you do not have a listing specifically for a divider, then DRAM frequency or RAM speed (or however you BIOS lists it) will determine the divider, based on the CPU's FSB and the speed you set RAM to. I.E., if you have a 266 mhz FSB CPU, then a corresponding RAM speed of DDR266 will give you 1:1 operation. If you have a 400 mhz FSB CPU, then the RAM set to DDR400 speeds will give you 1:1 operation.


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## Industrial

Quote:


Originally Posted by *NoAffinity*
What are you referring to? The system bus speeds tested were 133 mhz FSB and 166 mhz FSB. 133 is the stock system bus speed that a 533 mhz FSB CPU uses. This also produces DDR speeds of 266 mhz. Running 166 mhz FSB put the 2.53 used for testing at 3.154 GHz, and creates DDR speeds of 333 mhz.

Was that your question?

I was just confused becasue I thought you were doing all that to your computer and it looks to be far more powerful then 533mhz FSB. I guess I should have just asked if that was your computer or not. sorry


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## Flattit4

NoAffinity can u tell me how long the test for prime 95 cause i been test from yesterday morning untill now it's only 1.72%???


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## NoAffinity

Quote:


Originally Posted by *Industrial*
I was just confused becasue I thought you were doing all that to your computer and it looks to be far more powerful then 533mhz FSB. I guess I should have just asked if that was your computer or not. sorry









Oh...I was using a 2.53 GHz Northwood (533 mhz FSB CPU) for those tests, because 800 mhz FSB CPU's don't have a divider available to run the RAM faster than the CPU.









Quote:


Originally Posted by *Flattit4*
NoAffinity can u tell me how long the test for prime 95 cause i been test from yesterday morning untill now it's only 1.72%???

The general consensus is if you can run Prime continuously for 24 hours, then you're stable as a rock. I'm not completely sure about "1.72%", but I would assume that means the total Prime run has gone through completely once, and 72% of a second run.


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## Flattit4

Quote:

The general consensus is if you can run Prime continuously for 24 hours, then you're stable as a rock. I'm not completely sure about "1.72%", but I would assume that means the total Prime run has gone through completely once, and 72% of a second run.
what do you mean is if my cloking is no stabel after i run the prime it's gone fix the cpu to make it stabel its that right? anyway what is prime for?


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## NoAffinity

Quote:


Originally Posted by *Flattit4*
what do you mean is if my cloking is no stabel after i run the prime it's gone fix the cpu to make it stabel its that right? anyway what is prime for?

Prime is a stress tester. It will put a load on whatever component(s) correspond with the particular test you are running. If the test errors or fails, then said component(s) are not stable, and will require the necessary measures to ensure stability (more voltage, reduced clock speeds, better cooling etc etc).


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## Flattit4

Quote:


Originally Posted by *NoAffinity*
Prime is a stress tester. It will put a load on whatever component(s) correspond with the particular test you are running. If the test errors or fails, then said component(s) are not stable, and will require the necessary measures to ensure stability (more voltage, reduced clock speeds, better cooling etc etc).

oke thanks mate


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## aznchowboy650

how long does prime usually take?


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## NoAffinity

I think one full run takes a couple hours (of the CPU test, at least).


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## bumm

How do I know the timing of my RAM? Where can I see it? How do I set it?

How do I achieve 1:1?


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## NoAffinity

Quote:


Originally Posted by *bumm*
How do I know the timing of my RAM? Where can I see it? How do I set it?

How do I achieve 1:1?

You can find out what current settings are by downloading CPU-Z (www.cpuid.com), and checking the memory tab (see below).

You can find out what the rated timings are by googling the RAM part number. There should be a sticker on the RAM w/ the part number. Start at the manufacturer's web site, and if that doesn't turn anything up, then go to google.

Upload a CPU-Z screenie, and we can advise you where to proceed from there.


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## Sloth_Boy

This thread explains alot of useful info


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## ShawnMcGrail

Quote:


Originally Posted by *NoAffinity*
You can find out what current settings are by downloading CPU-Z (www.cpuid.com), and checking the memory tab (see below).

You can find out what the rated timings are by googling the RAM part number. There should be a sticker on the RAM w/ the part number. Start at the manufacturer's web site, and if that doesn't turn anything up, then go to google.

Upload a CPU-Z screenie, and we can advise you where to proceed from there.

whenever I try to check the mem timings through windows I can't see them? It won't detect the memory frequency either...


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## NoAffinity

Make sure you have the latest version of CPU-Z. You can always get them by running a Sandra test (memory bandwidth benchmark is a good one). It will be displayed about half-way down, in all the info under the bench comparison charts.


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## CesarWilkins

How can I enable 1:1 operation??







it is something in the BIOS?? I dont find anything like that, Sandra tell me that im in 5/4 operation...


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## NoAffinity

Quote:


Originally Posted by *CesarWilkins*
How can I enable 1:1 operation??







it is something in the BIOS?? I dont find anything like that, Sandra tell me that im in 5/4 operation...









Your board's an MSI? You want to set DDR (or RAM) speed to '266'. This will put you in 1:1. btw, why don't you have dual channel? Is your 1 gig only a single 1-gig stick?


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## Muhahahaha

I have PC2-4200 RAM (2X512MB) and was wondering what the loosest possible timings are. You say that for DDR the loosest timings are 3-4-4-8, but I have seen DDR2 memory with STOCK latencies higher than that (unless I am mistaken).


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## NoAffinity

Yes, DDR2 timings are looser, but I can't say that I'm complete up on DDR2 as of yet. Check your BIOS, and see what it offers.


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## hyde

Quote:


Originally Posted by *NoAffinity*

Quote:


Originally Posted by *
Originally Posted by CesarWilkins*
How can I enable 1:1 operation?? it is something in the BIOS?? I dont find anything like that, Sandra tell me that im in 5/4 operation...

Your board's an MSI? You want to set DDR (or RAM) speed to '266'. This will put you in 1:1. btw, why don't you have dual channel? Is your 1 gig only a single 1-gig stick?

I have the same question as CesarWilkins.. I'm in 3:4 though according to CPU-Z. can you help me?
And explain how to set it to 1:1 because I'd be happier if I actually understood it then just to have someone tell me what I should put for my situation


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## NoAffinity

Quote:


Originally Posted by *hyde*
I have the same question as CesarWilkins.. I'm in 3:4 though according to CPU-Z. can you help me?
And explain how to set it to 1:1 because I'd be happier if I actually understood it then just to have someone tell me what I should put for my situation









What speed RAM are you using? If you're in 3:4 (i.e. RAM is running faster than CPU), then you're fine. You only need to be concerned if you're in 4:3 (RAM is running slower than CPU). If you need confirmation, post a CPU-Z screenie, of the memory tab.


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## hyde

OK, thanks for helpin', here's the screen:










the spd-tab says it's max is 266 Mhz ..?

And how can I get it to 1:1 ?


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## NoAffinity

Yeah, SPD will report what it's rated to run. You are overclocking it, but as long as it's running fine, and it's not limiting your CPU overclock, then leave it where it is. 3:4 offers a little bit more performance than 1:1, if it's not limiting your CPU. If you want to put it in 1:1 in order to see if the CPU will go further, you will want to set RAM speed to 400 in BIOS (or there might be an actual divider setting, in which you will set it to 1:1







).


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## hyde

yaay i'm not doing anything wrong








ok great







thanks
rep for you


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## sprtsplyr3189

so i was reading this article and i haev a question. I have a 800mhz p4 2.8E processor with 1.5 gbs of pc3200 400 ram...which menas the ram operates at 200mhz right? if i set my fsb to 200, which is defualt, its a 2.8 and the ram is finely 1:1...that means im not oc'ing the fsb at all and if i up it even 1 then it owuld be 1:1 becuase the ram only goes at 200mhz..or can u make it run faster?? also.. the tighter timings means better performance right?


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## Xavier1421

Quote:


Originally Posted by *sprtsplyr3189*
so i was reading this article and i haev a question. I have a 800mhz p4 2.8E processor with 1.5 gbs of pc3200 400 ram...which menas the ram operates at 200mhz right? if i set my fsb to 200, which is defualt, its a 2.8 and the ram is finely 1:1...that means im not oc'ing the fsb at all and if i up it even 1 then it owuld be 1:1 becuase the ram only goes at 200mhz..or can u make it run faster?? also.. the tighter timings means better performance right?

Correct, you are at 1:1 at stock cpu speed. If you bump up the FSB to 201, and you have not put a divider on the ram via BIOS, it will still be 1:1. Tighter timings = better performance (usually)


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## NoAffinity

And yes, at 201 mhz FSB, you are officially overclocking DDR400/PC3200. At any given bus speed, tighter timings will offer better performance than looser timings, however FSB is king on Intel systems. Find max overclock at loosest timings first, _then_ tweak timings.


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## Oknilp

Haven't Overclocked much lately except a couple small presets, thought I'd make the rounds and freshen up a little wan't get ready for the team folding. 
Thank you much.


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## badillo69

Great thread


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## NipDar

CPUZ doesn't show Frequency or FSB/DRAM. Does that mean it is time for better memory?









Edit: Disregard what I just said and the attached thumbnails. I updated my version of CPUZ and it lists everything. Frequency is 133.3 Mhz, FSB







ram is 1:1, and timings are 2-3-3-6. The last thumbnail in the newest screen shot.


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## tankbusta

no pics boy and what version is that of cpuz


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## failure

hy.
i'm a very newbie and recently upgrade @ D820, http://tw.giga-byte.com/Products/Mot...8I865G775-G-RH and 512DDR pc32oo.
trying to speed up but i hit the wal at 3,12ghz and no mater vcore+ or change timmings dnt'n work







.of course something is wrong.
have an inteligent manager on my MB








--DIMM voltage control;
-- FSB voltage control;
..so on.
qestion: a decent oc is to 3,5?
how can i achive that? 
what i m do wrong?
thx a lot!


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## Stephant

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OK here is my 2 photo of cpuz. i wanted to go futher and how do i do it ? i added only 20fsb and running 3080mhz now. i am using @D820


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## JeremyFr

so let me get this straight I have a Cely D 346 533fsb and 512 of Kingston Value PC3200 DDR400. So if I wanted to run 1:1 then I would need to have the memory at 266Mhz in my bios? Is this correct? and also the "looser" settings is it easier for the ram to operate at "looser" than "tigher" i.e. I guess I'm trying to ask DDR runs more stable with looser timings though not as efficiently or as fast as it may have the possibility of, hence using the tighter timings?


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## GuDoN

Great thread, thanks for the detail.


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## Ravin

So I'm going to upgrade both my RAM and CPU sometime soon, and have a question that I have not seen anyone ask. I know that you can put higher rated RAM into a lower rated MoBo, and usually you can get the RAM to run underclocked.

Say I wanted to buy 1000MHz ram and run it at 800MHz speed. Would underclocking the RAM allow for tighter timings?


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## EAT

Hey guys NEED a little troubleshooting here. Had a guy I work with offer me a thousand more than I paid to build my rig, as long as It runs stress test for 24hrs or more. That was no sweat but I realized that I never bothered tweak my memory settings. So I started going through the paces trying to get stable at 4,4,4,12,1clock running at 800mhz maybe 900mhz. But for some reason I cant for the life of me get it to run through memtest on anything but auto voltage(1.85v) anything above that errors... With everything Ive read on the striker extreme this seems backwards. I feel that without hitting somewhat higher voltages that I wont ever get stability on anything but stock timings. The gigabit version of the 680i I had wanted at least 2.2v on the memory. What gives? I am a little pressed for time or I would have done some more research and posted a couple of pics. One thing I did notice was the famous asus vdroop from 1.31vcore to 1.248vcore in cpuz. Also at load drops from 1.31v to 1.28v think this has anything to do with my memory woes? Thought about trying the pencil mod but no time and if I get the memory to something semi respectable I'm plenty happy. Thanks in advance.


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## Nefarious79

Nice Writeup, I am going to play with this this weekend.


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## bobalobabingbong

Thanks for that!


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## xLightWorkerx

thanks for the info


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## Arnie'

Awsome guide for intel memory, is there an up to date version for DDR3 memory?


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## MAD-DUKE

...historic memory


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