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XMP and memory overclocking

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April 7, 2012 6:15:12 PM

I'm still a newbie when it comes to the more advanced sides of PC gaming and the word 'overclocking' still scares me. However, I recently upgraded from 2x2GB to 4x2GB Kingston 1333MHz/CL7 memory and noticed that though they advertise a latency of 7 that's only if you run it at XMP specs (1.65V).

Since I thought it was unfair of them to advertise a lower latency than I am actually running, I felt that I had to change it to 7. There were two options: switching to XMP, or manually changing the latency to 7-7-7-20.

Even though my memory is 1333MHz and my CPU is an i5 750 at stock speed (2.66GHz), I believe using XMP would be considered overclocking and therefore void the CPU warranty, is that correct? I know that doesn't really matter but I don't want to mess with my CPU just yet. If it is, I'd prefer manually setting the values in BIOS. However, when I tried that, the RAM voltage went up to ~1.78V according to my BIOS (EDIT: obviously because I have a kit of 4... stupid me). Should I manually change the RAM voltage to 1.65V (and/or try a CL of 8) or is the higher voltage not a problem? (I did notice that at stock speeds it already uses 1.54V instead of the advertised 1.5V...)

In short: I'm looking for some recommendations on how to decrease my RAM's Cas-latency to what it should be, in as simple and safe a way as humanly possible. Any advice would be appreciated!

(And once again: I am aware that I'm worrying over a lot of things that shouldn't be worried about, but I would really like to start at the beginning. Thanks.)
a c 347 } Memory
a b K Overclocking
April 7, 2012 8:25:41 PM

Running XMP will not void your warranty, especially not DDR3-1333. Anytime you set the RAM Manually always as part of it set the Rated Voltage. Further, keep in mind the Rated Frequency, CAS Timings, and Voltage only pertains for 'the' kit and not 'multiple' kit(s).

In the instance of multiple kits, plural i.e. non-match set and yes (2) kits are a non-match, you might need to sacrifice Frequency or CAS Timings. Example, your non-matched sets you might need to run them DDR3-1333 CAS 8-8-8-24 @ 1.65v~1.68v and add +0.01v~+0.03v to the QPI/DRAM (CPU IMC) Voltage for the kit(s) to work properly together. Trial and error followed by 4-passes to full day of Memtest86+ to validate the non-matched set(s).

Moreover, this is not always the case and depends on the Frequency + CAS. Anything (see graph) pink or below is considered very high performance and are indeed Frequency + CAS sensitive and rarely in (2) kits configurations work together without more extreme voltage tweaks (DRAM & 'QPI/DRAM/VCCIO/VCCSA/IMC' voltage increases.


Therefore, if the Rated is DDR3-1333 7-7-7-20 @ 1.65v then that's the values, all of them, that need to be set in the BIOS. Generally, the XMP sets a lot more timings than just Frequency, CAS (CAS-TRCD-TRP-TRAS-CMD), and DIMM Voltage.
April 7, 2012 8:56:00 PM

jaquith said:
Running XMP will not void your warranty, especially not DDR3-1333. Anytime you set the RAM Manually always as part of it set the Rated Voltage. Further, keep in mind the Rated Frequency, CAS Timings, and Voltage only pertains for 'the' kit and not 'multiple' kit(s).

In the instance of multiple kits, plural i.e. non-match set and yes (2) kits are a non-match, you might need to sacrifice Frequency or CAS Timings. Example, your non-matched sets you might need to run them DDR3-1333 CAS 8-8-8-24 @ 1.65v~1.68v and add +0.01v~+0.03v to the QPI/DRAM (CPU IMC) Voltage for the kit(s) to work properly together. Trial and error followed by 4-passes to full day of Memtest86+ to validate the non-matched set(s).

Moreover, this is not always the case and depends on the Frequency + CAS. Anything (see graph) pink or below is considered very high performance and are indeed Frequency + CAS sensitive and rarely in (2) kits configurations work together without more extreme voltage tweaks (DRAM & 'QPI/DRAM/VCCIO/VCCSA/IMC' voltage increases.
http://i1013.photobucket.com/albums/af254/Jaquith/CAS_Frequncy_Chart.png

Therefore, if the Rated is DDR3-1333 7-7-7-20 @ 1.65v then that's the values, all of them, that need to be set in the BIOS. Generally, the XMP sets a lot more timings than just Frequency, CAS (CAS-TRCD-TRP-TRAS-CMD), and DIMM Voltage.


Thanks for the thorough reply! I was under the impression that XMP automatically adjusted some CPU values that relate to memory and that even though there would be no effective change it would still somehow be 'registered' as overclocking. Judging by the chart, setting it to CL7 at 1.65V might not be such a great idea... so should I set the BIOS to XMP and let it do its own thing? Or should I manually set CL and voltage? Once again thanks for your quick reply!
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a c 347 } Memory
a b K Overclocking
April 7, 2012 9:12:41 PM

XMP doesn't do what you described, and about the deepest I'm aware is PLL Voltage.

Da what? "setting it to CL7 at 1.65V might not be such a great idea"

Q - What exact kit or kits do you have now?
I garnered 2 sets of 'some' 2x2GB Kingston 1333MHz/CL7 ; I am guessing KHX1333C7D3K2/4GX but the timings are 7-7-7-21 @ 1.65v
April 7, 2012 9:46:05 PM

Sorry, I should of course have mentioned that earlier. I thought I had 2 2x2GB kits of KHX1333C7D3K2/4GX as you said, but it turns out one kit of two is probably KHX1333C7D3K2/4G... which is pretty stupid as I thought I had made certain that I bought identical kits. Does that make a difference? And I thought CL7 @1.65V would be too much for 2 kits of 2 because it's in pink in the table...
Thanks for your advice.
a c 347 } Memory
a b K Overclocking
April 7, 2012 9:54:31 PM

It's tougher with mix-matching different IC's. If you look and answer the (2) questions then I can post the BIOS values for you to try.

Suggestion, use CPU-z and look at the Part Number for each DIMM using the 'SPD' tab:

Q - What are the values in the right most column for each stick?
Q - What exact MOBO do you have?
April 7, 2012 10:08:19 PM

For the KHX1333C7D3K2/4GX sticks, the right most column is XMP-1334 with 667MHz 7-7-7-20-34 at 1.65V, but the other two have an incomprehensible part name (9905403-115.A00LF) and show only JEDEC specs (right most JEDEC #4 685 MHz 9-9-9-25-34 at 1.50V). My MOBO is an ASUS P7P55D.
a c 347 } Memory
a b K Overclocking
April 8, 2012 1:56:47 AM

DDR3-1333 7-7-7-20 @ 1.65v
DDR3-1333 9-9-9-25 @ 1.50v
======================
DDR3-1333 9-9-9-25 @ 1.50v ; best possible 'mix'

Most RAM will work at 1.50v @ DDR3-1333; if you look in the 2nd column to the right I would assume there's a 1.50v @ 6XX MHz

In the BIOS simply set:
DRAM Frequency -> DDR3-1333
CAS Timings 9-9-9-25
DRAM Voltage -> 1.50v~1.55v
QPI/DRAM Voltage -> 1.20v or Auto
Save and Exit = Yes
April 8, 2012 11:13:31 AM

OK, thanks. So if I understand correctly I'm best off just leaving all settings as they are now. Because both kits are advertised at CL7 (the 4G at 1.7V and 4GX at 1.65V) I had hoped to lower the latency, but if that's not advisable I'll leave it at its default settings. Thanks for your advice.
a c 347 } Memory
a b K Overclocking
April 8, 2012 12:31:16 PM

Googling gave me this:
9905403-115.A00LF 2 GB DDR3-1333 DDR3 SDRAM (8-8-8-22 @ 609 MHz) (7-7-7-20 @ 533 MHz) (6-6-6-17 @ 457 MHz)

Upload an image of both kits 'SPD' tab.

Clearly & obviously, you have mix-matched kits and they won't perform faster 'reliably' as I've already stated. Further,much faster and you'll need to over-volt the 9905403-115.A00LF kit; you might be able to get away with DDR3-1333 8-8-8-22 @ 1.60v -- you can try it.
!