Which memory module takes precedent?

[LacquerHead]

I bought my T60 on the cheap, and it had only 512mb of installed RAM. I purchased a 1 gig stick and installed it yesterday. In a forum on this site I read that if you have two different memory modules, the pc runs at the speed of the slower one. Is there any truth to this, or am I really getting substantially improved performance with this setup?

[mybellyisempty]

substantially improved performance.

I went from 1gb of 667mhz DDR2 to 2gb of 533mhz DDR2 on one of my systems. The increase in performance due to more RAM far outweighed the different RAM speeds' performance loss could have made.

[pianowizard]

I bought my T60 on the cheap, and it had only 512mb of installed RAM. I purchased a 1 gig stick and installed it yesterday.

Do you know what speeds they are? If they're both PC2-5300 (i.e. 667 MHz), then there is nothing to worry about. If one of them is PC2-4200, then yes, it will slow down the other module but like mybellyisempty said, the impact would be hardly noticeable.