Probably an easy or dumb question

I have the Acer Aspire 9410 Series laptop with 1 Gig RAM installed (2 512MB sticks) I'm looking to upgrade my memory to 2 gigs or more. My question is if I buy a 2 gig stick can I replace it with one of my 512MB sticks and leave the other 512MB stick in with it so I would essentially have 2 1/2 gigs of RAM or do both sticks have to be the same?

Is it dual channel? You can, but for dual channel to work (double speed), you have to have the same memory in both slots. If you don't know, go get CPU-Z (Google it) and run that and see if it's running in dual mode or not (it should say Cannels # "Dual" in the "Memory" tab).

CPU-Z results on "memory" tab:

TYPE: DDR2
SIZE: 1024 MBytes
Channels #: Dual

DRAM Frequency: 266.0 MHz
FSB:DRAM: 1:2
CAS#: Latency (CL): 4.0 Clocks
RAS# to CAS# Delay (tRCD): 4 clocks
RAS# Precharge (tRP): 4 clocks
Cycle Time (tRAS): 12 clocks
Bank Cycle Time (tRC): 16 clocks

Ya, that's dual channel, you'll want two of the same type and size if at all possible. You can still do what you were thinking of, but dual channel will not work and performance will suffer. Just grab two sticks and put them in. You might have to do some fancy tricks to get access to the other slot if it's not on the outside... I'll check in a bit here and see how your memory slots are positioned. (busy @ work now)

http://www.acerpanam.com/synapse/forms/portal20.cfm?recordid=1186&formid=3425&website=AcerPanAm.com/us&siteid=7293&words=all&keywords=&areaid=7

Download the PDF, instructions on page 68 (you can look in the index and click on Memory > Installing)

Some laptops have memory limits of 2GB instead of 4GB. Make sure yours doesn't.

You would lose some performance (half of your memory speed) with 2 1/2 GB - either go for 2 or 4 (2 x 1 or 2 x 2) if you can.

http://en.wikipedia.org/wiki/Dual-channel_architecture

EDIT: And your laptop is 4GB max, I just checked: (thx for pointing that out, drumzorz)

http://www.acerpanam.com/synapse/forms/portal20.cfm?recordid=457&formid=3404&website=AcerPanAm.com/us&siteid=7293&words=all&keywords=&areaid=7

laptops these days can support asymetric dual channel, meaning mix and matching memory can still result in dual channel. i know i've done it on my laptop, i tried putting a1 gig stick with a 512 mb stick and it gave me 1.5 gb asynchronous dual channel.

to be honest though, dual channel or not, there probably wont be that big a difference in a laptop simply because ram is limited by the front side bus anyways.

Wow! thanks for all the great help everyone (especially n00b DevH'er). I've read in a couple of places now that there's very little noticeable difference between regular and dual channel but either way I have decided it's better to be safe than sorry. So I will be purchasing 2x1Gig PNY sticks from NewEgg for just under $40. Wish me luck and thanks again!

while you are at it, when you receive the ram, just install one of the two gigs of ram. if you open up cpu-z, you should still see dual channel, but it should say asymetric, and you should have a total of 1.5 GB.

Come back and post back results. Good luck!

Ok I'll do that. It may be a while before I order it though. I was reading that when it runs dual channel it only uses the smallest amount of either stick and the rest is run normally. So if I had a 512Mb stick and a 1Gb stick I would only have all of the 512Mb stick and half of the 1Gb stick running Dual and the other half of the 1Gb stick running normally. Is that true? I think I read it on Wikipedia

no clue, it makes sense though, not that it will matter with a shitty laptop's FSB.