Page 1
Intro

Page 2
Basics - RAM Timings

Page 3
Tweaking your RAM

Page 4
Updates & Final Words

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TWEAKING YOUR RAM

Now that you have a basic idea of what timings are, I will give some general guidelines on how to tweak your RAM.

Before I begin proper, I want to explain a little bit about RAM dividers, because this BIOS option is very important when overclocking.
 

RAM DIVIDERS

ABIT BOARDS

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Those who read my 1st article will remember this BIOS screen well. The option I will discuss here is the DRAM Ratio (CPU:DRAM) because this is the option that you will need  This option is very simple actually. All it tells you is the ratio between your FSB and RAM speed. The usual options are:

1. By SPD  - Sets the divider to the default ratio This usually means a ratio of 1:1.
    
2. 1:1  - This means that the RAM will run at the same speed as the FSB
    
3. 5:4  - This means that the RAM will run at FSB*(4/5) or in other words FSB*(0.8)
    
4. 3:2  - This means that the RAM will run at FSB*(2/3) or in other words FSB*(0.667)

ASUS BOARDS

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For ASUS board users, Set the AI Overclock Tuner to [Manual]. The option to adjust the RAM ratio is the DRAM Frequency option. Here are the settings:

1. Auto  - Sets the divider to the default ratio This usually means a ratio of 1:1.
    
2. DDR400 (which means 1:1)- This means that the RAM will run at the same speed as the FSB
    
3. DDR333 (which means 5:4)  - This means that the RAM will run at FSB*(4/5) or in other words FSB*(0.8)
    
4. DDR266 (which means 3:2)  - This means that the RAM will run at FSB*(2/3) or in other words FSB*(0.667)

DFI BOARDS

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For DFI board users, the RAM ratio is adjustable in the Advanced Chipset Features menu. The option to adjust the RAM ratio is the Memory Frequency For option. Here are the settings:

1. Auto  - Sets the divider to the default ratio This usually means a ratio of 1:1.
    
2. DDR400 (which means 1:1)- This means that the RAM will run at the same speed as the FSB
    
3. DDR320 (which means 5:4)  - This means that the RAM will run at FSB*(4/5) or in other words FSB*(0.8)
    
4. DDR266 (which means 3:2)  - This means that the RAM will run at FSB*(2/3) or in other words FSB*(0.667)

Did you understand that? Easy right? So, for example, if I have my FSB running at 250 MHz, and my DRAM Ratio at 5:4, then my RAM will be running at 250*(4/5) = 200MHz (or in other words 400MHz DDR)

OK, for those of you still wondering, when DDR400 means the RAM operates at 200MHz. DDR500 means it can operate at 250MHz. They are called DDR400 and DDR500 because they can transfer twice as much data per clock cycle. DDR means Double Data Rate. Get the picture? Good.

Now, to the fun part. Remember that I am assuming that you already know the maximum FSB that your CPU is stable at.

General guidelines for DDR500+:

Ok, simply said what you are gunning for is the highest 1:1 ratio when you overclock. Working with this RAM is the easiest:

1. Increase the DDR SDRAM Voltage to 2.8v (or 3.0v if your mainboard can do it).
    
2. Change the RAM timings to the highest latencies (3-4-4-8)
    
3. Set the DRAM Ratio to 1:1.
    
4. You should be able to reach 250MHz FSB speed with no problems. Some good quality DDR500 RAM can go up to 270MHz easily.
    
5. Once you are done with the overclock, Prime95 with the settings on this page to test the stability. If it runs stable for at least an hour, then you are done (this is assuming that your CPU is stable at those FSB settings). If there are errors, you will have to reduce the speed a little bit and test again.
    
6. After you find a stable setting, you may even want to tighten some timings a little bit to improve performance further. Just keep in mind that this type of RAM can hardly run at tighter timings. Experiment and run stability tests, play all your favorite games, benchmarks etc.
    
7. Remember that some DDR500+ RAM may not work at any divider other than 1:1 on some mainboards. Well, it seldom matters anyway because 1:1 is what you want with this RAM.

As you noticed, for DDR500, it is better to sacrifice some latency for more MHz.

General guidelines for DDR400 built for tight timings (2-3-3-7 or below):

Now, this type of RAM is a bit tricky to work with because it involves dividers, and a some mainboards are really picky when it comes to certain RAM brands and may not work properly with some dividers. However, this RAM is usually cheap and readily available. Here are the general guidelines for working with DDR400 RAM built for tight timings:

1. Increase the DDR SDRAM Voltage to 2.8v. You can increase it more if you like, but most DDR 400
    
2. You may want to test out the lowest timings/latencies it can do at default clockspeeds (200MHz). Lower the timings one by one and test out all the possible combinations to see which combination is stable. Run Prime95 torture test for at least half an hour for each setting you try out. Yes, you will have to spend a LOT of time on this one.
    
3. Once you have determined the lowest latencies your RAM can do at default clockspeeds, increase the FSB slowly and test the speeds at which it can operate at the tightest timings.
    
4. If your CPU can reach 250MHz FSB stable, then it is best to use the 5:4 DRAM Ratio. This means that the RAM is running at 200MHz.
    
5. If your CPU can reach 260 - 280MHz FSB stable, you might want to keep the DRAM Ratio at 5:4 and increase the latencies a bit to give more stability and best performance.
    
6. If your CPU can reach 280+ FSB, you might want to set the DRAM Ratio to 3:2 and keep the timings as tight as possible.
    
7. Prime Prime Prime, never forget to run Prime95 after changing any settings!

For DDR400/433 built for tight timings, the objective is to keep the timings as low as possible, (as close to 2-2-2-6 as you possibly can). This usually means keeping the RAM speed within the 200-220MHz region.

Prime95 Torture Test Settings - added Jan 30, 2004

1. Run only 1 instance of Prime95. This is different from testing your CPU where you should run 2 instances. It does not matter which logical CPU it is run on.
2. Run the torture test at the Blend setting. This mode will stress your RAM the most.
3. Right click the taskbar and open the Task Manager. Your Page File Usage should show a large number (for me it is 600+MB). Your CPU usage should show around 50% after it stabilizes. More than 50% is ok, but from my experience, it should not be constantly below 40%.

Some DDR400+ are very flexible, so you can follow either the DDR500+ guidelines or the DDR400 guidelines, whichever gives you better performance.

Remember that I cannot possibly go through all the possible combinations of RAM speeds and latency settings. The above are only suggestions/guidelines to give a basic idea. They are not rules that you MUST follow. Every stick of RAM is unique. The rest is up to you to experiment and find the best settings for yourself. You will have to spend a lot of time if you want to tweak it up properly. And please get yourself a good sticks of RAM. Working with cheapy RAM can be a real pain, performance wise and compatibility wise.

Look for the best compromise. Sometimes, increasing the latency by a little bit can allow you to increase the clockspeeds by a lot. This MHz increase may more than make up for the slight performance decrease introduced by increasing the latency. And sometimes, decreasing the clockspeeds a little bit can allow you to tighten the timings by a lot. The tighter timings might give you a bigger performance boost than the extra few MHz. Use benchmarks and games to see which gives you the best performance.

And I cannot say this enough: EXPERIMENT! EXPERIMENT! EXPERIMENT!
This is the only way those hardcore overclockers learn their trade. If you want to become like them, you will have to do what they do.

Next Page - Updates and Final Words

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Copyright© 2004 by Farhan Mohamed Ali