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My laptop has two slots for RAM, and currently has two 512 MB chips, for 1 GB. Windows XP is running terribly slow on it, so I want to upgrade the RAM. I could buy two 1 GB chips to replace both of the current 512 MB chips, to give me 2 GB of RAM. Or, the price is the same to buy one 2 GB chip, to replace just one of the 512 MB chips, and give me 2.5 GB total. The RAM it takes is PC2-4200 533MHz DDR2.

What do you think would be better: buying two 1 GB chips so it can take advantage of dual-channel operation, or buying one 2 GB chip to end up with more total RAM but not dual-channel operation? Like I said, price is the same, so performance is the only consideration.

I'm not doing anything especially intensive like video or photo editing -- just having multiple Office programs open, playing music, browsers, etc., but currently even opening the first application takes forever. If it matters, the laptop is a Toshiba Qosmio G25-AV513 running Windows XP Media Center SP3.

Thanks! Kevin

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up vote 5 down vote accepted

Well, it shouldn't matter TOO much, but using two similar strips of RAM would be recommended.

Just found you the Toshiba Qosmio G25-AV513 has a maximum support of 2 GB of ram so I would recommend buying two 1 GB strips or just use one 2 GB.

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I just checked the detailed specs and found the same -- thank you!! (I had looked in the User's Guide and it didn't say anything about the max.) I will replace both 512 MB strips with 1 GB strips. – pibboater May 22 '10 at 18:26

You need to have single stick or matched pairs of memory. Which you need will depend on the system and some systems can take either.

If the system can take either it doesn't really matter whether you buy two 1GB or one 2GB stick - assuming that the specs are roughly the same.

Putting the 512MB in with a 2GB stick probably won't work.

However, double check your system specs on the Toshiba site to verify which you need to buy.

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I agree now that using a 512 MB with a 2 GB wouldn't work because of the maximum of 2 GB as stated in the details specs. Although the reason I thought it would work is a friend had just one 512 MB chip in Toshiba Satellite A105, so he bought one 1 GB chip and it worked fine, recognizing 1.5 GB. (I had actually told him to go buy two 1 GB chips, but the guy at the computer store told him to save the extra money and just get one chip, saying he wouldn't notice much difference between 1.5 GB vs. 2 GB.) – pibboater May 22 '10 at 18:31
@pibboater - OK, I stand corrected in the face of evidence. – ChrisF May 22 '10 at 18:56

DDR2 modules must be used in matched pairs in modern systems.

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"must"? I don't think that's the case. Mismatched timing will just assume the speed of the slowest module. – RJFalconer May 22 '10 at 19:06
I've heard of system instabilities with mismatched timing, so I can't recommend to anyone that they try it. – Ignacio Vazquez-Abrams May 22 '10 at 19:08
I've had Dell computers that wouldn't boot unless the sticks were matched. – Rich Bradshaw May 22 '10 at 19:20

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