Just a simple step-by-step guide for new overclockers to easily overclock their DDR2 rams.

Note : Computers/overclocking is my hobby. Heck, I'm not even in the computer field. I'm just an average overclocker. Forgive me if there are incorrect facts....

Note x2 : I only know the very basic of RAM overclocking. You have to look elsewhere for RAM tweaking and advance overclocking settings....

Any recommendations/comments/incorrect facts, pls inform me through pm.

Index:
1) Introduction
2) Part 1 - Understanding ram settings
3) Part 2 - Ram multiplier/ratio
4) Part 3 - Vdimm
5) Part 4 - BIOS settings
6) Part 5 - Overclocking the RAMS
7) Part 6 - Stressing your rams to test for stability
8) Part 7 - Optimum setting after ram OC
9) Part 8 - Tweaking your rams settings
10) Part 9 - OCing 2 sticks vs. 4 sticks

-------------- Introduction ------------------------------

Remember:
Do this at your own risk
Overclocking can damage ANYTHING & EVERYTHING on your rig and may reduce the lifespan of certain parts
It is highly recommended to have:
- Heat spreader on your rams
- Active fan cooling directed on the rams
There are many other ways to OC your rams, this is only one of many ways

Note : Previous reviews on heat spreader for rams indicate that they don't actually result in higher OC. However, they are useful in keeping your rams at a lower temperature, which is important when you OC them.

Softwares that you need:
1) Memtest v1.70 (Get it here)
2) SuperPi v1.5 (Get it here)
2) Prime95 v25.5 (Get it here)
3) CPUz (Get it here)
4) Easytune5 (that comes with your mobo) - for other mobo, you can use their software.....

--- Easytune5 is used to increase the FSB. You can use any other software for this purpose

Note : Try to get the latest version for each software....

Hardware used in this guide:
Crucial ballistix PC2-6400 DDR2-800 2x1gb ram modules
Speed : 800mhz
Timings : 4-4-4-12
Voltage : 1.8 - 2.2v (Warranty is until 2.2v max)

C2Q Q6600 G0 stepping (9 x 266mhz = 2.4 Ghz)
- CPU multiplier : 9x
- Bus speed ----: 266mhz
- Stock voltage : 1.25v (may vary)

Gigabyte P35-DS3 mobo

Before you start:
1) Make sure your memtest is ok, that you can start your rig and boot into memtest straight away and NOT into windows
-- Look at their website, there are many ways you can start memtest, either by using a bootable CD, USB or floppy disk
2) Install 4 copies of SuperPI (for 4 cores), each in a different folder.
-- You would need to run 4 different copies of SuperPI in windows (to stress all 4 cores with the rams)
3) FSB and bus speed are usually used interchangeably, although strictly speaking, they are not the same

------------- Part 1 : Understanding ram settings---------------------------
There are many settings for DDR2 but we will limit to those few important ones

Ram speed
In mhz, e.g. DDR2-800 running at 800mhz
This is the parameter that you will OC, the higher the "mhz" the faster the rams

Ram timings
4 important timings : ---------------------------Effects on RAM performance -------
- CAS Latency (CL) ----------------------------- Large effect on performance
- RAS to CAS delay (Trcd) ----------------------Large effect on performance, higher for stability
- RAS precharge (Trp) --------------------------Smaller effect on performance
- Minimum RAS active time (Tras) ------------Very small effect on performance

Usually quoted in this format - CL, Trcd, Trp, Tras i.e. 4-4-4-12

Note - the Tras is usually a sum of the first 3 timings, or some people would set it to CL + Trcd + 2 (4-4-4-10) @ CL + Trcd only (4-4-4-8).....

Definitions used for timings:
Faster performance = lower timings = tighter timings = LOWER value
- 3-3-3-8 is faster than 4-4-4-8 which is faster than 4-5-5-9 which is faster than 5-5-5-15

Slower performance = higher timings = looser timings = HIGHER value
- e.g. 5-5-5-15

Question : Then why set higher/looser timings?
Answer : Higher/looser timings will allow you to OC your ram higher.
For example:
At 4-4-4-8, you can only OC max to 900mhz
At 4-5-5-9, you can only OC max to 940mhz
At 5-5-5-15, you can OC to max 1050mhz

Command rate
Either 1T or 2T

Usually quoted behind the ram timings e.g. 4-4-4-8-2T

For DDR rams, 1T is faster than 2T
For DDR2 rams, reviews up to now shows that there is no significant difference between 1T vs 2T in terms of speed

In terms of overclocking, 1T is like the ram timings, where your ram speed OC may be limited. 2T setting may allow your rams to OC higher....

Note : If there are new reviews on this, kindly inform me....

So, should I set higher frequency or tighter timings?
Refer here : http://forum.lowyat.net/topic/627600

The "trd" setting
Let's worry about this later, as it is an advance tweaking method....

For now, just know that the "Performance Enhanced" setting in the BIOS>MIT section apparently manipulates the trd setting (for gigabyte's mobo).
- 3 options - Standard, Turbo & Extreme

Set to "Extreme" to get the lowest trd setting.....

You can read more about trd here : http://www.anandtech.com/mb/showdoc.aspx?i=3208&p=6

------------------------------ Part 2 : Ram multiplier/ratio -----------------------------------------
There are many terms used which, more or less, has the same function:
- Ram ratio
- FSB:ram ratio
- Ram divider
- Ram multiplier

What it means is the ratio between the speed of FSB/bus speed and the ram speed

Example 1
Bus speed : 266mhz
FSB:Ram ratio : 3:5 (that means FSB is 3 as compared to ram speed which is 5)
Ram speed : 5/3 * 266mhz = 443mhz (but because DDR2 runs at x2, the actual speed is 443 x 2 = 886mhz)

Get it? It's just mathematics.....
Ratio of FSB to ram is 3:5
Ratio - 3 mhz : 5mhz
Then - 266mhz : 443mhz

Example 2
Bus speed : 333mhz
FSB:RAM ratio : 5:6
Ram speed : 6/5 * 333 mhz= 400mhz x 2 = 800mhz

Example 3
Bus speed : 400mhz
FSB:Ram ratio : 1:1
Ram speed : 1/1 * 400mhz = 400mhz x 2 = 800mhz

Example 4
Bus speed : 400mhz
FSB:Ram ratio : 5:6
Ram speed : 6/5 * 400mhz = 480mhz x 2 = 960mhz

For gigabyte mobo, it is the"System memory multiplier" option in BIOS.
- The options are : 2.0x, 2.4x, 2.5x, 3.0x, 3.2x
- actually less confusing as you can just multiply it with the FSB

Example 1
Bus speed : 400mhz
Multiplier : 2.5x
Ram speed : 400 x 2.5 = 1000mhz

Example 2
Bus speed : 333mhz
Multiplier : 2.4x
Ram speed : 333 x 2.4 = 800mhz

What's the use of the ram multiplier?
To set the rams at an optimum settings as compared to the CPU/FSB speed

Example
Crucial ballistix DDR2-800 2x1gb - Max OC : 970 mhz @ 4-4-4-12 @ 2.2v
C2Q Q6600 - Max OC : 3.0Ghz (8 x 400mhz)

So, at 400mhz bus speed, the optimum ram speed would be:
2.0x = 2.0 x 400 = 800mhz (nah, too low)
2.4x = 2.4 x 400 = 960mhz ( , this is the setting you want)
2.5x = 2.5 x 400 = 1000mhz (too high dude! )

--------------------- Part 3 : Vdimm -------------------------------
Vdimm = The voltage of the rams
Normal DDR2 vdimm = 1.8v
High performance DDR2 vdimm = can go higher i.e. 2.2v and above

Important : Even though rams have lifetime warranty, they also have vdimm warranty!!! For crucial rams, they give warranty up to 2.2v (although I have no idea how they can check if you burn the rams at higher vdimm )

So, how high should you set your vdimms?
Up to you lor, depends on how much risk you want to take
The higher the vdimm:
- The higher you can OC
- The higher the risk of damage
- The hotter the rams are

General recommendation (not a fixed value):
Value rams : 1.8 - 2.0v
Performance rams : 1.8 - 2.2v (or higher)

Ok, enough talk, let's start OCing your rams!!!

--------------------- Part 4 : BIOS settings -------------------------------
Start by going into BIOS - BIOS setting may vary with different mobo
For GA-P35-DS3, once your in the BIOS main page, press "Ctrl + F1".
- This will enable extra options in the M.I.T page
- For new bioses, you don't have to do this

Advanced BIOS features:
CPU Enhanced Halt (C1E) - disabled (for stability)
CPU EIST function - disabled (for stability)
Virtualization Technology - disabled
CPU Thermal Monitor 2 (TM2) - enabled (for safety purposes)

MB Intelligent Tweaker (M.I.T) features - make sure you have pressed the "Ctrl + F1" before entering this page

1) Reduce your CPU speed so that it doesn't OC above it's limits (when you increase the bus speed)

CPU clock ratio : 6x (from 9x)
-so, instead of running 9 x 266mhz (2.4Ghz), it is running 6 x 266mhz (1596mhz)

CPU Host Clock Control - Enabled (so that you can set the frequency)

CPU Host Frequency (mhz) - set to default 266mhz (This is your bus speed)

2) Keep your "System memory multiplier" at 3.0x
- ram speed = 3.0 x 266mhz = 800mhz (that's your ram's stock speed)

3) Set your ram timings to 4-4-4-8 (this is only enabled if you press "Ctrl + F1" in some older BIOSes)
- You can set it higher at 5-5-5-12 if you want (this will result in higher OC)

4) Set your vdimm +0.2v (1.8v + 0.2v = 2.0v)
- Again, this depends on you, on how much risk you want to take
- +0.3v to +0.4v would be my recommended max vdimm

Important : Reminder, have active cooling for the rams especially on higher vdimms....

5) Other bios settings
PCI Express frequency (Mhz) - 100mhz (prefereble not to put auto)

CIA2 - disabled (Important to set this, if not, your rig can auto-overclock itself)

Save your settings, reboot and load windows......

End result of the above settings:
Q6600 : 6 x 266mhz = 1596mhz
Ram : 3.0 x 266mhz = 800mhz @ 4-4-4-8 @ 2.0v

---------------------- Part 5 : Overclocking the RAMs --------------------------------------
In windows, run the following programs:
1) CPUz
2) SuperPI
3) Prime95
4) Easytune5

Note : I'm not at home, can't really check my Q6600 rig. I will reconfirm whether the settings below are correct once I get back home. Now CNY!!! That's why sooooo freeeee!!!

Run Prime95 first - Choose "Blend test" (no need to stop after this, let it run in the background)

Check CPUz, which will show your settings in BIOS:
CPU tab:
- Core speed : 1596mhz
- Multiplier : 6x
- Bus speed : 266mhz

Memory tab:
- Frequency : 400mhz (Remember that DDR2 rams are running at x2 bus speed)
- Timings : 4-4-4-8

Check Easytune5 > Overclocking button > Advance tab
- Look at FSB (that's your bus speed) : 266mhz
- This is where you increase your bus speed to gradually OC your rams
- Increase the FSB by 2-3mhz (your rams frequency will increase by ??, have to check)
- DON'T FORGET to press the "GO" button on Easytune5 to set the new setting
- Run 4 instances of SuperPI 2M test (Again, no need to stop prime95, let it run in the background until you get errors)
- If no errors and superPI completes its calculation, continue running prime95 in the background for 10 minutes
- if no errors on prime95, increase the FSB another 2-3mhz
- Run 4 instances of SuperPI 2M test again, then continue prime95 for 10 minutes
- Continue this cycle until you get errors (either in superPI or prime95) OR your computer hangs/reboots/BSOD

Summary : Increase FSB > Press "GO" to set > Run superPI 2M> Let prime95 run for 10 mins > If no errors, continue the procedure from "increase FSB".

Notes:
- 4 instances - means 4 copies of SuperPI running simultaneously
- While increasing the FSB, you can check on CPUz the corresponding changes in CPU core speed and RAM frequency.
- You can also run SuperPI 4M, 8M or even 32M. Just that it will take a bit longer to find your highest limit
--- Why not run SuperPI 1M? Can also, just that it takes time to start running all 4 copies of SuperPI!!
- You can also run Prime95 for more than 10 minutes. Again, it will take a bit longer to find your highest limit

Once you get errors/computer hangs/reboots/BSOD
Once you get a problem, look at the FSB and ram frequency when the error occured. This is over your ram OC limit.
Reduce the FSB by 2-3mhz
Restart the prime95 Blend test
Run 4 instances of SuperPI 2M
If no errors on SuperPI, continue Prime95 for another 10 minutes

If there are no errors, you have roughly found the maximum limit of your rams

Example
Errors at 303mhz (bus speed) @ 909mhz (ram speed)
Reduce to 300mhz (bus speed) @ 900mhz (ram speed)
Test to see whether there are any errors
If no errors, then 900mhz (ram speed) @ 4-4-4-8 @ 2.0v is probably the maximum OC for your rams at that specific timings and vdimm.


----------------------- Part 6 : Stressing your RAMs to test for stability ---------------------

Note the bus speed and ram speed where your OC is stable (Let's take 300mhz FSB @ 900mhz ram speed)
Return to bios and set it in the M.I.T page
- CPU host frequency (mhz) - 300mhz (so your rams will run at 900mhz)
Save and reboot
Boot into Memtest, and run it for 3-6 hours
If no errors, boot into windows and run simultaneously:
1) 4 instances of SuperPI 32M
2) Prime95 "blend test" for 6-12 hours

During this period, if you encounter any errors, you need to reduce the bus speed by another 2-3mhz (in BIOS)

How long should you stress the rams?
- There is no hard and fast rule on the duration
- Each section of testing can be shortened or lengthen, depending on how patient you are
- The longer the stress, the more sure you are that your rams are stable

Finally
Once you found the stability limit of your rams, you can do a few things:
1) You are happy at 900mhz @ 4-4-4-8 @ 2.0v
2) You want to OC higher. For this, you can:
-- Loosen the timings (e.g 5-4-4-9, 5-5-5-10)
-- Increase the vdimm (e.g. 2.1v or higher)
-- (See also Part 8 : Tweaking your rams)

-------------- Part 7 : Optimum settings after RAM OC ------------------------------------
Now, it's time to set your rig back to it's optimum settings
Don't forget that you put a 6x multiplier for your CPU at the beginning
- initially running at 6 x 266mhz = 1596mhz
- ending at 6 x 300mhz = 1800mhz (not optimum eh? )

So, how do you set your rig so that the CPU and the RAMs are running as near optimum as possible?

Here's a few examples of what to do:

Example 1
Stable ram OC : 900mhz @ 4-4-4-8 @ 2.0v
Stable Q6600 OC : 3.0Ghz
-- which you can run 9 x 333mhz, 8 x 375mhz @ 7 x 428mhz

If you run the bus speed at 333mhz, you need to set the rams multiplier to:
2.0 x 333 = 666mhz (Too low)
2.4 x 333 = 800mhz (stock speed, but you want to reach 900mhz, which is your stable ram OC)
2.5 x 333 = 832mhz (still not close to 900mhz)
3.0 x 333 = 999mhz (way over your OC)

So, the above settings is not that good for your OC as the best settings would be 2.5 x 333 = 832mhz which is still below your aim of 900mhz

If you run at 375mhz, your rams multiplier would be:
2.0 x 375 = 750mhz (Too low)
2.4 x 375 = 900mhz (Perfect!!!! )
2.5 x 375 = 937mhz (Over the limit)

That's perfect! You can run your rams at 2.4 x375mhz = 900mhz and your CPU at 8 x 375mhz = 3.0Ghz

What about 428mhz?
2.0 x 428mhz = 856mhz (Almost)
2.4 x 428mhz = 1027mhz (Way over the limit)

So, not a good setting.....

Example 2
Stable ram OC : 1000mhz @ 5-4-4-8 @ 2.1v
Stable Q6600 OC : 3.2Ghz
-- which you can run 9 x 355mhz, 8 x 400mhz @ 7 x 457mhz
-- The Q6600 probably can't run 7 x 457mhz due to the CPU FSB wall (in general)

If you run the bus speed at 355mhz, you need to set the rams multiplier to:
2.0 x 355 = 710mhz (Too low)
2.4 x 355 = 852mhz (Too low)
2.5 x 355 = 887mhz (still not close to 1000mhz)
3.0 x 355 = 1065mhz (way over your OC)

So, not a good setting....

If you run at 400mhz:
2.0 x 400 = 800mhz (too low)
2.4 x 400 = 960mhz (not bad)
2.5 x 400 = 1000mhz (Perfect!!! )
3.0 x 400 = 1200mhz (Way over the limit)

So, this is a good settings. Run the rams at 1000mhz (2.5 x400mhz) and the Q6600 at 3.2Ghz (8 x 400mhz)!

Note : Once you've set all the settings in BIOS, it is preferable to stress your whole rig by running Prime95 "Blend test" again, to make sure that your CPU OC and RAM OC are stable. This is especially true if you are setting a high FSB e.g. over 400-450mhz.....

--------------- Part 8 : Tweaking your rams settings ------------------
Let say that your rams are stable at : 960mhz @ 4-4-4-8 @ 2.1v
However, because of your CPU OC, you need to run your rams at 980mhz for best settings

In that case, like the recommendation above, either you:
1) Loosen the timings
- try to loosen the Trcd and Trp first, then only the CL (as there is a huge performance drop with the CL)
- e.g. try 4-5-4-9 or 4-5-5-9 before you go 5-4-4-9 or 5-5-4-10
2) Increase the vdimms
- e.g. to 2.2.v

The opposite is also true. If you need to run your rams at 940mhz for the optimum settings, you can:
1) Tighten the timings
- try 4-4-3-8 or 4-3-3-8 before 3-4-4-8 (unlikely)
2) Reduce the vdimms
- e.g. to 2.0v
3) Alternatively, you can tighten the timings while increasing the vcore to make the rams more stable at tighter timings
- e.g. 4-3-3-8 @ 2.2v


--------------- Part 9 : OCing 2 sticks vs 4 sticks ------------------
This is a frequently asked question.

In general, overclocking 4 sticks of memory modules is more difficult compared to 2 sticks. There are many reasons for this (what other sources say):
1) Not all 4 sticks can overclock the same
2) Put more burden on your memory controller (Northbridge) & motherboard
3) More heat generated (as there are 4 sticks and they are positioned closer together)
4) More noise, weaker signals in the FSB

Let's take a real life example. Say that you're training 4 bicycle racers for the Tour de France. Each one has its own different capabilities and expertise - i.e. strength, speed, endurance, mountain racing, etc. Because they ride in a pack, they ride at a speed that all 4 racers are capable/comfortable with. So, even though one guy can reach phenomenal high sustained speeds, he won't be able to do that due to the other racers in his team.

So, the same applies to the sticks of rams that you have. One may OC higher with looser timings, one may OC higher with tighter timings and one may not overclock that well at all. In the end, the speed and timings of all the rams would be limited to the stick that can overclock the least.

What if you have 4 sticks that are proven to individually OC to, let say, 1000mhz @ 4-4-4-8 @ 2.2v?
If you can get them to work together at that setting, then congrats! However, due to other factors mentioned above, it would be a difficult task without tweaking other settings like vcore, timings, Vmch, etc.....



----- Coming up ----
Confusion between FSB, system bus and bus speed.... me also confused

This post has been edited by kmarc: Jun 15 2008, 11:25 PM