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Should i add more slower memory?

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November 2, 2011 1:31:49 PM

So I never thought this day would come but I think I need more memory. This is my setup (what pertains to my question anyway :) 

ASUS PX58D Premium motherboard
Intel i7 920 – overclocked to 4ghz
6 GB Corsair Dominator 6 GB (3X2 GB) 1600 MHz – CAS 8

When I bought this memory 2 years ago, it cost me about $250 and it was supposed to be some of the best triple channel memory available; and it truly was. I have never had any issues even after all the overclocking abuse. In any event, I wanted to upgrade to at least 12 GB so I thought of buying the same exact memory, which is still around $100 for 6 GB. But when I started looking around, I noticed that an additional 12GB of memory is about $70! So I did some research and the latency is not as good (9 as opposed to 8) but could there be much difference between that and my memory?

The specific brand I’m looking at is Kingston (KHX1600C9D3K3/12GX(XMP) which by the way is one of the models in the QVL for my motherboard). Newegg is selling a 12 GB pack for $79 before a rebate. Would I be able to add those 3 - 4gb – sticks to my computer to have a total of 18 GB without problems? I understand that the RAM performance of the other 6GB will be hindered by the higher latency of the additional RAM but overall, is more-slower memory, better than less- faster memory in terms of performance, overclocking, etc?

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a c 347 } Memory
November 2, 2011 2:35:41 PM

I don't recommend the mixing, so either use the Kingston by itself or get the better Corsair. The issue is mixing CAS timings and completely different IC's, plus topping it off with the burden of higher densities.

DDR3-1600 9-9-9-27-2N @ 1.65v
DDR3-1600 8-8-8-24-2N @ 1.65v
========================
DDR3-1600 9-9-9-27-2N @ 1.65v ; worst of both sets

Sure you can try running both sets at DDR3-1600 9-9-9-27-2N @ 1.65v followed by extensive Memtest and Prime95 + Blend to test for both errors and stability, but it's again nothing that I would do. If necessary by meaning of errors, increase the DRAM QPI/VTT Voltage to 1.30v~1.35v and test again.

Failure at DDR3-1600 frequency try DDR3-1333:
DDR3-1333 8-8-8-24-2N @ 1.50v~1.55v


Good Luck! :) 
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November 2, 2011 7:16:26 PM

Hey, many thanks for the quick response. I had a feeling it wasn't the greatest idea but i just don't want to waste the memory that I already have in there.

I found this other 12gb deal from Patriot for ~$100: Patriot Viper Extreme (PX7312G1600LLK) that seems to have closer latency. 8-9-8-24 @1.65v would that be better?

Also, if I decide to get rid of the corsair memory I have and decide to buy 2 Kingston sets to have 24 GB total, (aside from reliability) will that be better in terms of performance?

The way i see it i can either add a max of 12 extra GB (4gb in each remaining slot for a total of 18GB) with CAS 8 for $100 or I can buy 24GB CAS 9 for about $150.

One additional factor is that the 24 GB Kingston set (exact model actually) is in the ASUS QVL. Patriot, Crucial or any other manufacturer for that matter, doesn't have any "supported" memory past 12GB using the 6 slots.

Thanks again for taking the time to respond! :) 
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a c 347 } Memory
November 2, 2011 10:36:58 PM

Again I don't recommend the mixing, so either use the Patriot by itself or get the better Corsair.

I'm assuming what you have now is either TR3X6G1600C8D or CMP6GX3M3A1600C8 - IMO get the SAME KIT.

Unless you are running Rendering i.e. Adobe Premiere or have some Huge (5GB+) database I cannot imagine you running low on RAM.

IF you have (less than) <75% Used Physical Memory, see below, you are fine. Otherwise sure you need more.

Resource Monitor (example 26% used):
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November 3, 2011 12:57:46 PM

Good deal. Yeah I decided to just get a 24GB corsair package that, although a bit slower, is supposedly very reliable and compatible with my board.

Funny you should mention rendering and databases, I use AutoCAD and run databases from my computer for work (not over 5GB though) but sometimes while this is going on, i will encode video or play video games. I have looked at my resource monitor and the RAM usage can get >75%

I am positive that at this point 24GB is way overkill but I feel that this will ensure that if I ever feel i need more memory, I will just have to build another computer (hopefully not in the next 5 years) and for the price of that much memory, I figured - why not?

Thanks for your input jaquith. I greatly appreciate it.
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a c 347 } Memory
November 3, 2011 3:23:52 PM

Yeah CAD, Rendering and in my case huge SQL database require huge amounts of RAM to process quickly.

Don't worry about DDR3-1600 CAS 8 vs CAS 9. When the densities goes way up 4GB or 8GB/DIMM often low CAS coupled with high frequency won't work or work with excessive errors. In 24GB about the fastest I would go is DDR3-1600 CAS 9.

IF you have problems: 1. Not all memory is recognized {BIOS look for Memory Configuration Protect and -> Enabled}, 2. Voltages: DRAM Voltage -> spec~spec +.05v and/or DRAM QPI/VTT Voltage -> 1.25v~1.35v.

BTW - Many i7-9XX can actually run 48GB of RAM; Intel uses the same lithography as the Xeon and 6x8GB has been proven to work. Apprarently, Intel overlooked invoking a limit.

Good Luck! :) 
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November 3, 2011 3:47:45 PM

Best answer selected by solutionMaster.
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a b } Memory
November 4, 2011 7:28:20 AM

This topic has been closed by Maziar
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