ram in matching pairs

i just purchased an Acer Aspire AS9300-5349 Laptop Computer and i am upgrading the ram because it only came with 1gb (512x2). i've looked around and noticed that you can either buy in pairs or 1 stick at time. For about the same price i can get 2 1gb sticks or 1 2gb stick. if i purchased the 1 2gb stick i'd take out 1 of the original 512 sticks and replace it with the 2gb stick. my question is if i were to buy the 1 2gb stick and install it with 1 of the original 512 sticks would if be faster than buying the 2 1gb sticks and installing them? sorry for the long post and thanks in advance

 

2GB + 512MB is faster than 1GB plus 1GB. They both run in Dual channel. And while the dual channel when running 1GB x2 is slightly faster than running in 2GB 512MB, It won't be by much. And more ram is (almost) always better.

 

What he said...

 

I disagree fabarati, 1GBX1GB could in theory be taking from each stick all the time (100% thereby making use of the 128 bit bus 100% of the time. In the real world will never work out that perfect. With 1GBX2GB theoretically 67% of the time can take advantage of 128 bit bus. 512MBX2GB Theoretically 40% of the time can take advantage of 128 bit bus. I've said theoretical while not real world they are proportional. At some point you get diminishing returns not much more size and slower performance. If 1GBX2GB is 10% slower than 1GBX1GB, I suspect 512MBX2GB is at least 15%. The 10% is from SiSoft Sandra benchmarks which I believe only uses 512MB so in real world memory intensive tasks I suspect bigger hit.

The only benefit from the extra 512MB is if you need it but the slow down in speed is constant, people should think about that.

 

Well, since it runs in dual channel (asynchronus dual channel) the performance hit is not as large compared to normal Dual channel. And dual core CPU (or at least intel ones) don't benifit MUCH from dual channel. And added ram is always nice, especially if he has vista (don't know about that one)

 

From all I've read about memory. Matched pairs that are designed for dual channel work better than just single 1 gig sticks.

This place has quite a bit of information on memory. Also here. Should be able to find the answers your looking for.

 

3 words. Asynchronus Dual channel.

I always wanted to say something like that,

 

asynchronus dual channel is Dual channel, so the latter comment that Dual Cores don't benifit much is not correct unless you mean running w/1 stick of RAM because if you run 2 sticks you are running dual channel of some form and at some level if the MoBo supports.

 

Just something I read Chaz say. I did look it up, but can't remember what or where.

But It was that if you have a dual core, dual channel does not increas performance by that much. But this might just affect Intel CPU's.

 

powerpack is 100% correct finally someone who understands the theory behind how ram works .

The reason there isn't a big gain is becasue ram speeds are now incredibly fast compared to FSB. Unless your running single channel ram at less than your FSB frequency the FSB is the bottleneck not the memory. Hence if you have a 667mhz FSB and single channel 667mhz DDR ram you have already theoretically hit your max and dual channel shouldn't help at all except for maybe less latency. But if you have 800mhz FSB you should notice about a 10 - 15% gain from going to dual channel. But like powerpack said if your doing Asynchronous dual channel such at a 2gig & 512mb sticks you only get 40% of that 15% so about 6% increase.

Note:
Everything I'm saying is theoretical and in practice it won't work exactly like that but it should be similar. You will probably see worse results but you might see better (the real world does funny things).