Memory Timing 7 replies

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Kwould

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#1 11 years ago

I have 4 GB's of OCZ "SLI" DDR2-800 memory. OCZ claims that it's included EPP sets the default voltage to 2.1V and has a default timing of 4-4-4-15 1T. According to my BIOS (which is up to date), my memory is booting at 750Mhz as opposed to 800Mhz, is receiving 1.9V and is timed 5-5-5-15 2T. I have manually adjusted the voltage to 2.1V; everything is cool there. When I try to manually set the timing to 4-4-4-15 1T, it won't boot. Furthermore, I manually set the frequency to 800 and it boots at 750 anyway. My motherboard has the nVidia 590 SLI MCP, so it's EPP ready. Can anyone tell me what the problem is, or what I'm doing wrong? If there is other pertinent information regarding this matter that I'm leaving out, please let me know.




EtherLaser

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#2 11 years ago

I don't own an AM2 PC, but have you turned EPP off? Cos if not it could be resetting the values to what's stored in the EPP profile. Try turning it off if you haven't done so and try to run it at 4-4-4-15 1T then. Hope this helps. Sam




Kwould

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#3 11 years ago

I just tried that and it hasn't worked. I appreciate it though. I did figure out the problem with the frequency however. It is only booting a 750Mhz due to my odd numbered CPU multiplier (15x). I suppose 750 is good enough. I could overclock it, but I wouldn't get it all the way up to 800. Meanwhile I still have the timing issue. Any other ideas?




C38368

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#4 11 years ago

How many sticks? Two or four? AFAIK, AMD's memory controller still has the 2T bug when using four sticks. If you have all four slots filled, drop the timings but put the command rate back at 2T and see if it works.

If not, give us more to work with!




Kwould

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#5 11 years ago
C38368;3735837How many sticks? Two or four?

I am using four sticks, But I bought each set at seperate times and was presumably having the problem before adding the second set, as the timing and command rate were the same then. I just haven't tried to address the issue until now. I managed to get it to work for a few minutes at 4-4-4-15 1T with the MA and MCLK drive strength cut in half. There was a noticeable difference in boot time, however I received the BSOD shortly after.

...drop the timings but put the command rate back at 2T and see if it works.

I was always under the impression it was the command rate that made the big difference so it never occurred to me to try that. Thanks. I will give it a shot and get back to you.




C38368

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#6 11 years ago

Command rate does have a huge impact on performance. It's essentially the number of cycles any given memory command (from the controller) must be sustained for before being executed. At 2T, every command will require two cycles before being executed. For this reason, 1T at a lower frequency is almost always measureably faster than 2T at a higher speed.




EtherLaser

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#7 11 years ago

I also remembered after an article on DDR2 frequencies in AM2 PC's, that the maximum frequency you can get from the RAM before overclocking is taken from your CPU frequency divided by a whole number (in your case 3000/4 = 750Mhz). I'm unsure as to wihch number is used depending on CPU. Sam.




Kwould

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#8 11 years ago
C38368;3735837AFAIK, AMD's memory controller still has the 2T bug when using four sticks.[/quote] I am currently going back and forth with OCZ tech support, and they say there is also a timing limitation when using 4 modules. They concur that there is a 1T limitation and that I should "give it a try anyway". My BIOS says that I need to reduce the MA & MCLK drive strengths in order to realize 1T. Any recommendations? [quote=WildHeart_Sam;3737350]I also remembered after an article on DDR2 frequencies in AM2 PC's, that the maximum frequency you can get from the RAM before overclocking is taken from your CPU frequency divided by a whole number (in your case 3000/4 = 750Mhz). I'm unsure as to wihch number is used depending on CPU. Sam.

I found a chart on another forum that cross-references CPU multipliers with bus speeds and memory frequencies/dividers (very helpful). I could play around with all the numbers, but the simplest way would be to get the FSB to overclock to 213Mhz stable. It would get the memory close (798.75 Mhz). Any voltage settings or other recommendations on how to achieve this?