XMP memory on AMD - settings

[bfollett]

I have XMP-1600 cas 8 memory on my gigabyte amd 880 motherboard. The SPD for the memory shows cas 8 for XMP, but cas 9 for a standard 800 mhz bus, which is what my motherboard chooses to use by default. I went into the motherboard bios and manually selected 8-8-8-24-34, to match what CPU-Z showed as the xmp memory timings, but there are additional setting in the bios that I don't know what they should be set to. Here they are with the defaults for cas 9 in parentheses

1) TWTR command delay (6T)
2) TRFC0 (110ns)
3) Write Recovery (12T)
4) Precharge (12T)
5) RAS to Ras Delay (5T)
There is also a 1T/2T command timing that is defaulting to 2T, although it doesn't show any default in the spd.

Should any of these be changed with Cas 8? Any help would be appreciated. FYI, the system is running stable with the changes I have made so far.

Thanks,

Bob

 

[cpillin425]

Hi, I can't believe nobody answered your question. lol Well anyway I had some instability with my Gskill Ripjaws model F3-12800CLD-4GBRL, because I am running two kits for a total of 8GB. These aren't even listed on my motherboard's QVL in the manual. I tried several different timings and settings in the BIOS like 8-8-8-24 @1.5V. ,1.6, and 1.65v, they would still crash, even though they would check out OK in memtest86+ after testing all night. That's when I opened up CPU-Z and saw that there was a table in the SPD tab of CPU-Z. So basically what this means is that these are the JDEC standards for your particular RAM brand and model. If you are running an INTEL CPU, then you would enable the XMP setting in the BIOS and you would be good and solid stable. BUT if your are running an AMD Phenom II (as is my case) you will ALWAYS need to put the settings in manually in the BIOS. AMD chipsets/processors are not capable of running XMP by default. You will need to look at either the JDEC or XMP timings and input them manually into the BIOS. For example, I set the XMP timings in cpu-z manually, which were 9-9-9-25-33-2t @1.5 V. To answer your question (depending on what brand of cpu/motherboard you have) if you have an AMD cpu, then you would set the XMP timings manually in the BIOS, you do not need to worry about the other settings, just set those that are there and be sure to set the speed manually to 1600 and you are good to go. Open up CPU-z and make sure the settings match. You can see your current settings in the "Memory" tab in CPU-Z. phew, hope that answers your question that was posted back in January lol.