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I mostly just use laptop for streaming movies and Iplayer, and the usual e-mail,facebook etc. 2x2gb to replace the existing 2x1gb is around £40, my question is really if 6gb is better, (1x4gb & 1x2gb) which is available as a kit from OWC america $119.99 but then you have to pay import tax etc.(hassle)

Seeing as 1x4gb & 1x2gb isn't a matched pair for duel channel mode does it matter if the ram is bought as a pair or not? (providing there from same manufacturer and: 200 Pin SO DIMM DDR2 PC2-5300 667MHz?

Global Memory do a 6gb kit for £99 (Amazon & ebay)-are they any good?

Mr Memory you can get the same 4gb & 2gb as single's by selecting them, so don't think it would be a kit for £75 (don't know the brand either)-are they any good? what should I go for? (To have my macbook run best for longest, currently using Lion 10.7.5, avoiding buying new one for as long as possible, also should I revert back to Snow Leopard?)

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Shopping recommendations are not allowed on Superuser, per the FAQ. – ChrisN Jan 5 '13 at 23:00

1x 4GB & 1x2GB isn't a matched pair for duel channel mode. Does it matter if the ram is bought as a pair or not?

It usually does not matter.

You can mixed different brands and speeds of RAM and they should operate at their lowest common speed. Should being a keyword. Usually they do. And mixing them often means mixing two different speeds and not using the full potential of one of them.

(Think of it as buying a 50kmph car and a 60kmph card. But when you ride as a convoy both are limited to 50kmph)

As for what is better, it depends on your needs.

  • Two same sized DIMMs in dual channel mode yields slightly higher memory speeds. If memory servers that means your computer is about 5% faster on average. The speed gain will be most noticeable in programs which do a lot of memory accesses.
  • More memory (6GB total vs 4GB total) also help.

Which helps more depends on how you use your computer. I expect the the 6GB combination to be the best, but as said it really depends on your use.

One more example:

  • You start a ray tracer which accesses memory a lot. Say this one uses 2GB. Faster memory will help here. ( 2GB used from 'fast' 4GB vs 2GB used from 'slow' 6GB )
  • You compile a port and use 5GB. 5GB 'slow' memory will be much faster then 4GB fast and 1GB swap.
    ... etc etc.
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I'm a total novice, you lost me completely with the second example. Are you saying for my usage, (as mentioned in my initial question) I should go for the 1x4gb & 1x2gb from Mr Memory? Thanks for your help. :) – Gareth Jones Jan 5 '13 at 23:11
I tried to be as generic as possible in order to answer all similar questions and not just yours (which is -or is close to- a shopping question). And the answer was 'faster mem is nice, more memory is usually better'. And ofc. more and faster is even better. -- For merely watching movies there should not be much difference. As in, you probably can not notice the difference without a stopwatch. – Hennes Jan 5 '13 at 23:33

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