Fact or Fiction regarding memory upgrading?

I was discussing with a co-worker about upgrading to 1.5 GB of RAM, (by removing one of the two 512 card slots and replacing it with a 1 GB slot, leaving the other one put and totalling to 1.5 GB). I did that with my old DELL Inspiron and it seemed to work well, except for the overheating ( but that was b/c of the model....5160).
He mentioned he read and heard that if you upgrade you should upgrade both slots, with them being identical sizes, memory. EX.If you want to upgrade to 2 Gigs, get two 1 gb slots.etc
He said not doing so, in regards to what I want to do with mine, affects performance in a negative way.
Thoughts, ideas please.

 

not true. you are free to upgrade however you like.

 

True, for all notebooks with dual channel memory controllers. Using different size SODIMMs forces single-channel mode which cuts your memory bandwidth in half. Real-world that doesn't make for as dramatic a performance drop as you might think but it's best to buy matched pairs.

If your notebook is old enough to have a single-channel memory controller then buying matched pairs won't help performance.

 

If your tasks require a lot of memory page accesses and swaps then it will negatively effect performance and you should get 2GB of matched 1GB pairs. If you mostly just browse, use office applications, and light multimedia, then don't worry and just go for the extra 512MB.

The dual channel explanation from Brian is exactly right. The question you should be asking yourself is, do your applications require a steady stream of data to/from the memory that goes past that supplied by a single channel. That includes both for use by the CPU, and also DMA from hard drives, optical drives, and video cards.

 

clarification:

early gen mbs required matched pairs to run dual channel. this is no longer true. you can run mismatched pairs and still get "flexible dual channel" results.

you do not need matched pairs

 

Well I have a fairly new Vaio SZ 110. It came with 1 GB of RAM. Was thinking of tossing one of the 512MB and getting a GIG. Then maybe in the future tossing the other 512MB getting to 2gb. but for now 1.5 gb would be fair. I plan on getting the new Microsoft Flight Simulator X. I downloaded a demo and already see with the 1GB I have that it wont be enough,even though it runs quite smooth. Butbesides that I use it for net,e-mail,and mostly iTunes playback.
I ran a crucial memory scan and it recommends getting a 200-pin SODIMM DDR2 PC2-4200. So I assume I have a 200-pin SODIMM now. So I dont think I would be getting diff types the way you are discussing. It woldjust be one larger memory with the 2nd being 512mb

 

Your coworker is right, for the most part. All the specifications between the two SODIMMS should ideally be the same, but the memory size... I'm not sure if that matters.

 

Drumfu, do you have any documentation on that? I must have missed something there. Are we seeing this in all the major chipsets these days?

 

You can put in two different sizes. Older motherboards used to complain when you did this, but new ones are more flexable and don't have a problem.

 

Look, in todays computers, the more RAM the better. Dual channel, in laptops, only offers a 3-10% performance boost. People who say you have to have matched pairs or an "even" number of RAM (ex 512mb, 1GB, 2GB) dont have any idea what they're talking about. I use 1.5GB in my laptop right now and the performance over 1GB is very noticible. Most of my PC's over the last few years have had "strange" numbers of RAM even.

 

I agree with Twilight vampire. I would rather worry about not having enough ram than any tiny differences with dual channel.

 

Funny, yet scarey how SONY sells their 1 GIG Module for $599 @ Sonystyle.com