Model A1311 / Late 2009 / 3.06 or 3.33 GHz Core 2 Duo processor

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Is it OK to install one 4GB memory card.

I want to upgrade the memory to 8gb. I could buy two 2gb cards for the extra slots, but is it OK to fit a 4gb card to one slot? I'm thinking that I can add another 4gb later if I need to.

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Many thanks gents, just what I needed to know.

David

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RAM Type: PC3-8500 DDR3 Min. RAM Speed: 1066 MHz

Details: Supports 1066 MHz PC3-8500 DDR3 SO-DIMMs (204-pin).

Standard RAM: 4 GB Maximum RAM: 16 GB

Details: By default, 4 GB of RAM was installed as two 2 GB SO-DIMM modules. Two slots free.

Andy is somewhat correct is is referring to interleaving and is preferred but not as essential as it once was.

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@mayer - I agree interleaving memory is less of an issue in newer hardware systems (DDR4). But, in this system it does help as the memory bus is slower.

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Buying the single 4 GB is the way for exactly the reason you said, it leaves a slot to add more RAM again down the road.

But, remember that if you add a second 4 GB stick later it should exactly the same as the first. Pairs of RAM should always be identical.

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Very true! I've seen some very odd issues when the modules are not the same. When one puts in a different sized module there is no risk of bad memory timing. But if you put the same sized modules in you'll confuse the system.

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With RAM prices right now, it is sometimes cost-prohibitive for certain PC builds to contain kits of two sticks. This especially impacts the budget audience. A lot of forums online -- and I was guilty of this up until about a year ago -- will strongly urge PC builders to strictly use RAM modules in multiples of two. This is to enable dual-channel platform capabilities, which will utilize 2x64-bit channels on the memory bus (128 data traces on the motherboard going to the IMC) instead of one. This effectively allows our memory to double its maximum theoretical bandwidth by working in parallel, since each stick can only push 64 bits of data at any time.

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Jim, when we discuss identical pairs of ram, the two modules must also have matching CAS latency values, correct? I've had people tell me it doesn't but that doesn't seem right to me

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Yes, Both Row Access Strobe (RAS) & (Column Access Strobe (CAS) really need to match. In the old days even that sometimes wasn't enough which is why you wanted the same lot as well as different lots had variations which could mess you up. Today, chip manufacturing has come a long way! But people forget the old module they are trying to reuse maybe off when matched up with a newer module.

As to the reason, this can gets a bit strange as the issue is not so much a slow access problem but too fast! The faster module will beat the slower one but the memory bus may not ready for it before the other has finished so the data it's holding expires.

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David Samways will be eternally grateful.
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