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Understanding memory timings and overclocking

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November 8, 2011 9:30:59 PM

Hey guys, sorry for 'yet another noob post,' but I am very curious to further understand memory timings and how to alter them and / or the speed of the RAM (I refer to both as 'overclocking' - not everyone does when it comes to timings) in order to ensure a more stable system.

I will start by stating that I have an MSI P67A-GD65 mobo, 8gb (2x4gb) Corsair Vengeance RAM, i5-2500k (OC'ed to 4.6 ghz), zalman CPU cooler, GTX 560 super-OC (manufacturer OC), tx850W PSU, 500 MB, 64 MB Cache WD HDD.

I understand the basics, mainly after reading this article: http://www.hardwaresecrets.com/article/Understanding-RA...
However, my question remains as to how I can figure out the best possible set-up for my system. Is it simple trial & error, benchmark, compare, repeat? Also, I have XMP-support enabled, and my memory is running at ~800 Mhz with 9-9-9-24 T2 timings. I have read throughout the internet (mainly here on the forums) that lowering the bus speed of your RAM can increase CPU OC stability. If I lower my RAM bus speed, I would lower the timings - correct? (lower bus speed = able to do more in (x) cycles?)

I apologize for all the sporadic questions, but they are kind of what I was asking myself while reading (teaching myself) about the RAM timings and how they affect performance. I am comfortable changing voltages and settings, so I have no problem in testing things out.. Also, I cannot get my computer to run in Dual-Channel mode.. I've tried everything - switching to every possible DIMM slot (with 1 and 2 sticks to ensure they all work) and my DIMM slot 3 seems to be giving me a hard time..

Also - with the P67A-GD65 comes the OC-Genie button.. It's an auto-overclock but I can still alter the settings - Should I disable this in order to have a completely stable machine? I feel like it's overclocking things I don't know about (configures the best settings on it's own) and while I'm trying to overclock things myself, the settings changed by OC-Genie may be causing instability?

Thanks for reading the wall of text - enlighten away!
a b } Memory
a b K Overclocking
November 8, 2011 9:54:44 PM

OC'ing is strictly tiral and error, which is why many folks get frustrated. No one can tell you exactly what settings will work for your hardware once you go beyond the default speeds.

When you lower the RAM frequency it makes it easier for the memory controller - which is located in the CPU these days, to operate more easily/reliably than it can at a higher frequency. Also when you slow the RAM timings it gives the memory controller more time to perform the operations than with lower latencies.

Since OC'ing the CPU frequency delivers better performance gain than OC'ing the RAM, it's usually better to OC the CPU and keep the RAM close to the default frequency - but each CPU/mobo/RAM combo is different and that's why you must make a change and test for stability to see what works for your CPU. I use OCCT for a quick stability check.

Yes it would be best to disable OC Genie and make the manual BIOS changes yourself - recording what you change so you can go back as necessary.
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November 9, 2011 11:48:56 AM

Oh I understand that nobody can tell me the best settings for my system - which is what makes overclocking fun, there's no looking it up on the internet and just setting it to certain settings that are labeled as 'the best'.

As for my memory settings - is XMP good to have enabled? I also am still unable to run my computer in dual-channel RAM mode.. however, in the MSI control center it has the RAM voltaged to 1.6533 V (OC Genie). Could this potentially be why my computer won't start in dual-channel? I tried lowering the V to 1.5 - standard, and my memory's default, to no avail.. It honestly seems to be something with my DIMM-3 on-board..

Also, say I lowered my RAM speeds (that would mean taking off XMP support) and timings - would I get better performance? The CPU could work easier and faster, but the RAM would be a bottleneck for the PC, wouldn't it? Considering the RAM works at lower speeds, albeit with lower timings as well but then again it could do more in less timings..

I am going to disable OC Genie from here on out.. Thanks!
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November 15, 2011 1:22:24 AM

Bump -- anyone able to help explain?
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November 15, 2011 3:15:04 AM

To run your RAM in dual-channel mode your sticks should be in slots 1/3 or 2/4. If 3 is a problem use 2/4 and you should be in dual-channel. The Motherboard manual usually shows these layouts if your not sure. I've read that sandy-bridge doesn't like 1.65v RAM theres a way to work out the safe limit i think its something like cpu volts +.5 +/-5% but I can't remember exactly. Also from what I've read above 1600mhz the benefits of frequency increases aren't as good so you might wanna set it all to stock, then slowly increase volts to see if you can tighten the timings.
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November 15, 2011 3:19:47 AM

Ah, okay - so with higher voltage I can run lower timings? Why exactly does that happen? And my manual said that 1&3 / 2&4 should be dual-channel.. Neither successfully boot - tried cmos clears constantly with different minor adjustments to see if the board is just giving me a hard time - I'm beginning to think my DIMM-3 is dead.. It won't boot up with just one single stick in the DIMM3 slot.
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November 15, 2011 3:38:24 AM

Yeah sounds like your mobo is having issues, IMO RMA your motherboard. Having dual-channel is probably going to increase memory bandwidth by alot more then any overclock. I should state that I didn't overclock my ram as it already runs at 2133mhz using xmp, but i believe timings changes works like regular overclocking, pump more volts through and you can make stuff faster :p 
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November 15, 2011 5:13:43 PM

Ah, okay - I will do some last-minute troubleshooting and be sure to RMA the mobo if that is certainly the issue (don't want to go through all that hassle if it's the RAM or something else causing the problem).

If I were to lower my timings - currently 9-9-9-24, would I lower the rest of the RAM timings? Such as the many other options (not just your average x-x-x-xx). If so, how would I know what to set them at, or would I not change them at all?
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