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Need a bit of help on memory

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October 19, 2010 5:46:09 PM

Every three years or so I sit down to build a new computer. I am no expert and do not follow all the changes between builds. My starting point is the September 2010 build for $1,000 article. For the sake of these questions assume I use the computer for gaming and I generally run one program at a time. I wander into Newegg and look at the item and similar items, compare prices and read through a few reviews. That being said I put my wish list together and get this far:

ASUS P7P55D-E Pro LGA 1156 Intel P55 SATA 6Gb/s USB 3.0 ATX Intel Motherboard

Intel Core i5-760 Lynnfield 2.8GHz LGA 1156 95W Quad-Core Desktop Processor BX80605I5760

MSI N470GTX-M2D12-B GeForce GTX 470 (Fermi) 1280MB 320-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card

Microsoft Windows 7 Home Premium Upgrade

Now the last time I did a build with trusty Windows XP, I was reading about the memory limitations for the 32 bit version of XP which I own. For this build I wanted to jump up to a 64 bit os with the intent of taking advantage of more memory. So I started looking at memory ( I like Corsair) and along the line I read some articles, tried to look up what memory would go well with the above choices, got a blistering headache and realized I was totally lost. Let me ask some simplistic questions to get me back on track:

Reading about the i5 I see mention of two channels for memory. Looking at i7 I read, “Intel Core i7 enables three channels of DDR3 1066 MHz memory” and wandering through Corsair products I see they sell these 3 packs of memory sticks for the i7. Now does that mean that if I use the i5 with two channels, it will only work (note the word phrasing) on two memory sticks?

Same question as above but change the wording to: recommended you use only 2 memory sticks.

Or should I just not get hung up on the channel thing and fill up the 4 memory slots?

So going on I look at the mb and see under memory “DDR3 2200(O.C.)/1600/1333/1066”, so I am thinking DDR3 1600 sounds good (I do not overclock). Going back to the i5 in the fine print I see, “The Integrated Memory Controller optimizes data bandwidth with support for two-channel DDR3 1066/1333 memory.” I assume I am limited to 1333 by the chip? As such getting DDR3 1600 would be a waste? I was looking at:

CORSAIR XMS3 8GB (4 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model CMX8GX3M4A1600C9

Let me round this out with a generic question. I use the build for gaming and seldom run multiple programs. The board will handle 16GB. Windows 7 will handle 16GB. Don’t see a spec on the chip, maybe not relevant. There is probably some point where you don’t get much bang for your buck by adding more GB. Where should I be shooting for in GB?

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a b } Memory
October 19, 2010 6:30:46 PM

4GB of RAM will be enough for you. The ideal setup is 2 x 2 GB. If you wanted to go for 8GB, then look at 4 x 2 GB sticks. However as you rarely run more than 1 program at once it would be overkill.

Also the RAM should run at 1.65V or less. These days 1.5V or less should be easy to find, especially at 1333 MHz.

To answer your questions: the i5 will work with 1, 2, 3, or 4 sticks of RAM. The preferred setup is an even number (2 or 4 sticks) to take advantage of the "dual channel" architecture. And between those two options, 2 sticks is preferred - e.g. 2 x 2GB is preferred over 4 x 1GB. However, differences are slight.

As far as speed goes, unless you OC or make other trade offs such as disabling the CPU's Turbo, you will not be able to run the RAM at 1600 MHz. With an i5 and no OC ambitions look at 1333 MHz RAM that runs with timings / CAS rating of 7 (sometimes written CL 7). CL 8 is slightly slower but not terribly noticable so depending on the price difference you could fall back to 1333 CL 8's, or even another step back to CL 9's.

That being said, there are good reasons for getting 1600 frequency RAM:
1. You might OC in the future
2. You might use the RAM in a future build that supports faster frequencies
3. The best reason is that sometimes 1600 RAM is the same price - and sometimes even cheaper - than 1333 RAM.

A couple points - you can run 1600 RAM at 1333, and in your board it will default to that. Also 1333 RAM can still be OCed, sometimes to 1600 or faster. But there is no guarantee. 1600 RAM is simply RAM that the manufacturer guarantees can reach that speed.

There is very little real world difference between 1600 and 1333 RAM. I'll find a link and add it in here.

One other point for clarification - where you say i7 above, those statements are true if you further specify i7 9xx CPUs. The i7 8xx CPUs are dual-channel, they use the same socket and motherboards as the i5s.

EDIT: Here's an article you may find worthwhile: http://www.tomshardware.com/reviews/core-i7-870-1156,24...
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October 21, 2010 5:51:59 PM

Thank you ekoostik for your on point reply, very helpful.
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October 21, 2010 5:52:12 PM

Best answer selected by Bobbarry.
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a b } Memory
October 22, 2010 3:21:00 AM

You're welcome. Good luck with your build.
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