Multiple questions about DDR2 RAM

Question

1. Does dual channel work with a 32-bit operating system or will I need to install a 64-bit operating system in order for it to work?

2. If I had 2x 512MB 667 MHz and 2x 1GB 667 MHz, both in dual channel mode, will both pairs work together, and will they still all work as dual channel even though the two pairs are of different size? (each pair is on separate channels)

3. How do I know where to put the pairs? Do you always put both pairs in the same colored slot, or is it supposed to be 1 pair in the green and brown slot and the other pair in the other brown and green slot?

4. Do you think there's much difference in speed between a 533 MHz DDR2 and 667 MHz DD2? Is it worth buying? Cost is not a problem, I currently have 533 MHz and Front Side Bus is 800 MHz if that helps.

Answer 1

1. Dual channel is a feature of the chipset/motherboard and is independent of the operating system. I first used it in Windows XP Pro on a Pentium 4.

2. This may not be dual channel. Some motherboards support different modules, but, many do not - it is best to have all modules the same, and frankly, you can buy it so cheap now (4GB ~£25), it is not worth the aggravation.

3. Each socket should be numbered as socket 1, 2, 3, 4 or bank 1, socket 1, 2, bank 2 socket 1,2. In either case, the first pair is 1/3, second is 2/4.

4. The cost is so minimal, if you are buying new, I would get the better, or even DDR2 800. However, the speed difference in real world scenarios is tiny.

Answer 2

1. No, dual-channel is a hardware feature to increase memory bandwidth. Current x86 microprocessors use 64-bit memory interfaces. Dual-Channel offers 2x64-bit so actually a logical 128-bit interface. In fact it's just the CPU accessing two (64-bit-) modules in parallel.
2. This depends on the CPU. Usually you should take care that each channel is equipped with the same amount of memory. Check your mainboard manual on information which slot belongs to which channel. For example if slot 1+2 belong to channel 1 and slot 3+4 belong to channel 2 then make sure you install the 1GB modules in slot 1 and 3 and the 512MB modules in slot 2 and 4. This way each channel is equpped with 1.5GB.
3. See answer to question 2. You need to check the mainboard manual to know which slots belong to which channel.
4. There is not a huge difference between DDR2-533 and DDR2-667 in practical application (not speaking about pure memory benchmarking tools). In fact it's much more important to have sufficient amount of memory than to have fast memory. In case you run out of memory the system starts to swap which is anyway MUCH MUCH slower than the most slow memory you can put in your system. So if your choice is to put either just 2GB of DDR2-667 or 3GB which works at DDR2-533, then I would recommend using 3GB in any case.

Answer 3

One question at a time per the FAQ, but here goes...

Does dual channel work with a 32-bit operating system or will I need to install a 64-bit operating system in order for it to work?

No need for 64-bit for DDR2. For more than 2GB you can make some registry edits or do some other things...discussed here. Not a factor on DDR2, is a factor on size.
There are work arounds.

If I had 2x 512MB 667 MHz and 2x 1GB 667 MHz, both in dual channel mode, will both pairs work together, and will they still all work as dual channel even though the two pairs are of different size? (each pair is on separate channels)

Sort of...both will be utilized, but possibly not to the same degree. Depends on the motherboard implementation. Better than not having it either way though.

How do I know where to put the pairs? Do you always put both pairs in the same colored slot, or is it supposed to be 1 pair in the green and brown slot and the other pair in the other brown and green slot?

Same size and speed should be in similarly colored slots. Faster/bigger should be in the primary slot(check your motherboard documentation for which is slot0 and which is slot1...maybe slot1 and slot2 depending on how geeky the manual writer was...)

Do you think there's much difference in speed between a 533 MHz DDR2 and 667 MHz DD2? Is it worth buying? Cost is not a problem, I currently have 533 MHz and Front Side Bus is 800 MHz if that helps.

If you add 667 to a board where the other bank is running at 533, most of the time both banks will run at the one speed...probably the slower one. If they choose the faster one, go into the BIOS and set it manually. I have seen fewer errors and dead hardware from underclocking than from overclocking. Both happen though.