Memory Voltage.....what do i set?
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The question of memory voltage comes up a great deal, i will try to explain the best way to find the optimum voltage you need and explain why you will see 2.1V DDR2 or 1.8V DDR3 when in some cases we will advise you to test and run lower than this.
OCZ qualify memory on many boards, for the sake of this guide i will talk about 8000 Reaper X 4GB, take this though as all our memory with the references to voltage etc covering all our product.
8000 Reaper X
http://www.ocztechnology.com/product...pc_4gb_edition has specifications that say 2.1V operating voltage. The reason for this is as follows.
OCZ test and qualify the memory on many different boards, not all boards need 2.1V for the memory to work well, but some do. Because of this we have to state the highest needed voltage that was needed for the modules to work as advertised, often though this is NOT needed. So board A needed 1.85V but board X needed 2.1V, to make sure A and X work with everything in between we state the voltage for board X.
Now this also covers OCZ a little as yield at any given voltage can go up and down. This means over the life of the part the quality of the IC's may get better and require less voltage to run at 1000MHZ or may get worse and require a little more voltage to run 1000MHZ.
So why do OCZ forum staff ask you set ONLY the voltage the memory needs and not just set this max voltage as stated on the website?
We do this knowing in many cases there may be no need to run the voltage that high. Many boards (high end) have awesome memory overclocking and usually operate at much higher frequencies at lower voltages...hence we advise you test and ONLY set the voltage that is needed to be stable.
So why do some boards work better than others?
Many of the top enthusiast boards overclock memory very well, the reasons for this are the PCB's and components used on the motherboard have been tuned to keep memory signaling as clean as it can be, this in turn means it is able to run at higher frequencies. This is why top flight enthusiast boards are more expensive than mid range channel boards ( which usually focus on feature set over overclockability)
These enthusiast boards also feature settings which allow much finer tuning of the memory voltages, timings and clock signals. This makes it possible to fine tune memory at higher clocks using less voltage.
I thought just adding more voltage helped memory overclock?
It does, but there are 2 ways to get the memory doing what you want.
1 Fine tune the clocks and timings using the options in bios.
2 Force more voltage to the clocks and memory and use brute force to make it work.
Now obviously option 1 is what we want end users to adopt, the reasons for this are mainly it helps to ensure a long a productive life for the memory, and it produces less heat which can actually mean it runs better.
Overall you can either just follow the specs that came on the packet or off the website and set that voltage; or you can fine tune using that voltage as a base to start and set the voltage the memory actually needs to run and no more. Be aware though many boards actually overvolt by default, if you set 2.1V in bios you may be actually supplying 2.2V or higher to the memory. Also the AUTO setting does not usually set 1.8V DDR2 or 1.5V DDR3, it normally set quite a bit higher than this. On some boards I have seen as high as 2.0V for DDR2 and 1.78V for DDR3 all hidden behind the AUTO setting.
If you are running ANY type of Intel or 680/780i chipset DDR2 motherboard with 2x2GB for 4GB or 4x2GB for 8GB of ram, tRFC will have a major impact on how your system will run.
you may see option for tRFC called "Refresh to activate delay" so please don't be fooled. If your bios only goes as high at 42 you are going to have issues with speeds much over 900MHZ, in some cases some boards even have issues at 800MHZ.
We have changed SPD on many of our 2GB modules to set tRFC to 54 leaving the bios option at Auto, you do NOT need this SPD if your motherboard has this option in bios and it sets higher than 42, only ask for this update if you have a board that sets 42 or lower AND you can supply the SPD file to us off the modules you have showing a tRFC values of lower than 54 clocks.(we will supply the tool that allows you to send SPD to us)
tRFC has a massive impact on stability with 4 and 8GB kits due mainly to the massive increase in density and the way the memory has to be refreshed, most boards were originally setup for 1GB modules, this is the reason why some set tRFC to low for 2GB modules to work well.
Please if you have bought a 4GB kit and you are having issues look for tRFC in bios and set to at least 54 Clocks, in many cases you will see that you can lower voltage to the memory quite dramatically....
I've been experiencing similar difficulties with 4x2gb of OCZ2RPR10664GK modules.
Things I've learned (so far):
1. The relationship between DRAM Voltage, MCH Core, and tRD is very touchy. You just need to play with combinations of values @ stock frequencies; and eventually you'll get there. Once you establish a solid baseline, you can try to overclock your system from there.
2. You'll probably need to set your DRAM voltage near the upper limit of the rated voltage for your modules to run 4x2gb. My max rated v is 2.30, and I've determined my "Sweet Spot" is at 2.24v-2.26v.
3. Add to MCH core slowly. I've found that immediately jumping MCH up to 1.2v is not a good idea. Try 1.6 and then 1.8 first. From trial-and-error experience, I've learned that too much MCH is just as bad as too little.
4. Try "loosening" your DRAM timings a bit. My rated timings are 5-5-5-15, but I'm not stable (so far...) unless I set them to 5-5-5-18.
5. Use MemTest86+ as your first stress-test evaluation of a settings scenario. If it passes that, move on to Intel Burn (set @ maximum to make sure most of your 8gb is utilized...) If that passes, only then move on to prime95 testing. The concept here is to gain confidence that your DRAM is stable before committing to a 12hr. p95 test.
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