Few really simple questions about RAM.

Which RAM you need to buy depends on your system. Are you building your own system? If Yes then list other hardware to people can better help you with what type of RAM you need to buy. This will be a lot easier then trying to explain all the different types of RAM.

it sounds like what you're after is some term definition and how they apply, so here goes: DIMM = dual inline memory module. This replaced the much older single inline memory modules. All notebook memory for any models released within the last several years is going to be SODIMM (small output DIMM) SDRAM basically signifies that the memory is of the standard type and not RAMBUS. Again, any notebook you get will use SDRAM So really the only decision you have to make is between DDR and DDR2. DDR is slower but has less latency (the amount of time before something gets read or written to the memory), and DDR2 has more latency, but runs at faster speeds. Something you might want to consider is that currently DDR2 is less expensive because it is used in most new systems. And the newer the system, the faster the memory you can get. Notebooks with Yonah or Merom CPUs (Core Duo or Core 2 Duo) can use DDR2 memory up to 667 Mhz. Notebooks with Sonoma CPUs (Pentium M w/533 Mhz FSB) and Turion CPUs can use DDR2 up to 533 Mhz. Pervious models using Pentium M, Pentium 4, & Athlon 64 CPUs can use DDR memory up to 400 Mhz. and make sure you know for sure which kind of memory your system takes, because DDR will not fit in a DDR2 slot and DDR2 will not fit in a DDR slot. dual channel means that if you have 2 memory modules of the same size, they will work together and make your memory speed up to twice as fast, although the actual speed that you can use is limited by the motherboard FSB. Because of that, it's nice, but is not nearly as useful or groundbreaking as it may sound. Shared means that the graphics card or chipset uses some of the system memory for graphics. if you do not plan to play games on your computer or use anything that takes up a lot of memory, this should be fine. however, if you want to play games or do anything that needs a medium to high level of graphics performance or if you will need every bit of memory that you can get, then I would suggest getting a notebook that has dedicated graphics memory, so the graphics card will not use the system memory.

1. Dual Channel = you have two identical sticks of RAM, and the system optimizes usage so that both sticks are used evenly, resulting in faster, parallel accesses.

2. Shared = there is no such thing as "shared" RAM. As you stated, this refers to the GPU using part of the RAM as video memory. Stay away from computers like this unless you only use your laptop for browsing the internet and writing Word docs/PPTs.

3. DDR = Double Data Rate RAM. Until recently, the only type of RAM AMD-based laptops used.

4. DDR2 = Double Data Rate RAM, rev. 2. This is NOT backwards compatible with DDR. All new computers should be using this RAM.

5. DDR2 with SDRAM = I have no idea what this is, but it sounds like the guy posting this has no idea how to use technical terminology.

6. DIMM = Dual Inline Memory Module. It is a fancy term for a stick of RAM. In the past, there used to be SIMMs as well, but pretty much you only get DIMMs now.

As for tradeoffs:

(a) Speed vs capacity: For example: 1gb of DDR2-667 vs 2gb of DDR2-533. Go for capacity. A lot of times, the lower latencies on the DDR2-533 will make up for the speed differential.

(b) Dual channel vs Single channel: In order to get the benefits of dual channel, the two sticks of RAM in your laptop have to be near identical. This usually implies same company, specs, etc. However, dual channel benefits are overrated. For example, let's say your laptop has 1 stick of 1gb RAM. Now, someone has given you a stick of 512mb RAM for free (or you got it for a really good price). Or, you get another 1gb stick, but it has different specs (latencies, speed, etc). Go ahead and stick that RAM in there. The rule of thumb is that all the RAM will run at the lowest common speeds, and all DDR and DDR2 RAM is backwards compatible (ie, you can use 667mhz or 800mhz RAM in a 533mhz system without any problems).

As mitcity22 stated, once you start figuring out which laptop(s) meet your requirements, it will be easier to decide which RAM configurations are appropriate for it.

Regards,

zakaluka2.