RAM compatibility.

[RLT69]

Oh good grief!

This is not hard to understand and underscores the need to do actual research. Read the manual/documentation! It explains much of this information. Yes some of it is confusing and I will attempt to clear this up.

1. AMD processors support both DDR2 and DDR3 ram. That is why the documentation lists RAM speeds for both DDR2 and DDR3. Which ram (DDR2 vs DDR3) you use depends on the motherboard socket (AM2 v AM3). AMD attempted to make the transition from the old AM2 socket to AM3 easy by making their processors backwards compatible. Thus one processor can support either DDR2 or DDR3 ram depending on the motherboard.

2. The motherboard (MB) determines the type and speed of ram you buy, not the processor. Read the manual for the MB and check out the MB web site. It will list the maximum supported speed, type (DDR2 vs DDR3) and tested manufacturers. Buy ram according to what the MB supports not the CPU.

You can buy ram with speeds faster than what is supported by the CPU. The CPU will only use the speed it supports. Thus if you have ram that is 1800mhz and the CPU only supports 1066mhz, the ram will only operate at 1066mhz.

Why would you buy faster ram? Because you might upgrade your processor and the new processor might support the faster speed.

Build for tomorrow.

3. CAS latency/timing is determined by the voltage. That is why you will see two or more voltage and timings listed for ram. Ram can support multiple timings.

Example: 5-5-5-18 @ 1.95V vs 4-4-4-12 @ 2.1V.

One setting is considered the stable setting; you wont' have issues installing your OS and your OS will be stable. The other is considered the "less stable" setting; you may have problems installing your OS, your system may be unstable.

As long as the MB supports one of the voltages, typically the one with the slower timing, you can use that ram. Again read the MB documentation and check the list of supported ram. Buy ram that is similar in specs as the ones on the list. You don't have to buy exactly what is on the list. The ram supported list is meant as a guide.

Hope that helps.

[A Traveller]

Ok, thanks RLT69.

[usually_quiet]

I neglected to mention at Intel's i5 processors, but as it turns out they too only support DDR3 up to 1333 MHz.

It isn't simply a matter of what has been tested by the manufacturer. There are technical reasons related to performance for why Intel and AMD don't officially support memory running at higher speeds. I read a couple of articles and some reader comments made about them, and to the extent I could follow, the reasons made sense.

From what I could understand, unless the processor is overclocked, installing higher speed memory than the manufacturer supports doesn't improve performance. All you've done is waste money which might have been better spent on something else. My only consolation is that the memory I bought was on sale, so at least I only wasted a few dollars by purchasing it.

There is no point in buying for the future unless you like to upgrade every year. If a new processor or motherboard is only going to be needed two or three years down the road, chances are that by then the memory available will be better, cheaper and faster, and more of it will be needed than is already installed.

[RLT69]

@usually_quiet

I'm sorry but your post is incorrect.

1. No one is suggesting that RAM speeds that are faster than what is supported by the CPU will make your system faster. That is untrue. As I said, RAM will only operate at the speed that the CPU will support.

2. You don't *NEED* to get a new motherboard (MB) every year. Your MB will support a long list of processors and will be good for several years. Unless you have the money, most people don't buy the most expensive processor. You buy the the one you can afford, typically the slower model, and after awhile when prices drop you upgrade to the faster model as your needs demand.

Example: My wifes new system supports both Dual Core and Quad Core processors. We bought the Dual Core processor but eventually we will upgrade to the Quad Core processor. We spec'd out the memory according to what our upgrade needs will be.

3. Memory always drops in price. Unless there is a shortage in raw material, prices drop. You'll never get the best deal. As soon as you buy your ram, within the next couple of months the prices drop. Fact of life.

4. Speeds increase over time but that does not mean you need to get the fastest speed nor does that mean there is a MB that is stable enough to support it. Honestly can you tell the difference between DDR3 1800 and DDR3 2200?

Example of RAM prices:
DDR3 1800 - Kingston 4GB (2x2GB) $109
DDR3 2000 - Kingston 4GB (2x2GB) $108
DDR3 2300 - G.SKILL 4GB (2x2GB) $279

Even if your MB supports DDR3 2300, unless you can afford it, you are not going to buy DDR3 2300. You'll buy DDR3 2000 or DDR3 1800. Eventually DDR3 2300 will drop in price. But are you going to sit around and wait for the price to drop when you want/need to build a system today. You buy what you can afford.

5. The amount of ram MBs support will change over time but not drastically. Most MBs support 16GB and have for a long time. There some that are starting to support 32GB.

The point is the ram you buy today will be good tomorrow even if you buy a new MB. This will help defray the cost of building a new system in the future. Then when you have the extra cash, and your MB supports it, you can go out and buy the faster memory.

Your new MB should be good for several years. Unless you have lots of cash, no one goes out and builds a new system every year. Honestly there is no point because there isn't that much changing.

The next major builds aren't going to happen for 3 or 4 years:

DDR4, which won't be released until 2012 and probably won't be mass supported for a year or two after.
http://en.wikipedia.org/wiki/Synchronous_dynamic_random_access_memory#DDR4_SDRAM_.28proposed.29

USB 3.0 Commercial controllers are expected to enter into volume production no later than the first quarter of 2010.
http://en.wikipedia.org/wiki/Universal_Serial_Bus

PCI Express 3.0 specification to be finalized and released by second quarter of 2010. New PCI Express 3.0 compliant devices available by 2011.
http://www.mydigitallife.info/2009/08/24/pci-express-3-0-specifications-release-pushed-out-to-2010/

So you are looking at 2013 to have all 3 technologies on MBs in mass production.

Hope that helps.

[usually_quiet]

@RLT69 Not everything I said was directed at you, but here is my reply anyway.

1.

"No one is suggesting that RAM speeds that are faster than what is supported by the CPU will make your system faster. That is untrue. As I said, RAM will only operate at the speed that the CPU will support."

"It isn't simply a matter of what has been tested by the manufacturer. There are technical reasons related to performance for why Intel and AMD don't officially support memory running at higher speeds. I read a couple of articles and some reader comments made about them, and to the extent I could follow, the reasons made sense.

From what I could understand, unless the processor is overclocked, installing higher speed memory than the manufacturer supports doesn't improve performance."

That was not a reply to anything you wrote. The first part was directed at the OP. I had read some things written by people who overclock their processors, and that is all the 2nd part is about. I don't overclock, so I had to take their word for it. If you are saying the 2nd part is not true, I can't agree or disagree.

2.

" You don't *NEED* to get a new motherboard (MB) every year. Your MB will support a long list of processors and will be good for several years. Unless you have the money, most people don't buy the most expensive processor."

I said "like to upgrade every year", which we both agree would only pertain to people who don't mind paying for the privilege. While it is a reply to something you said, I did not in fact say "you need a new motherboard every year", though some people would say they do, and a very few actually would.

"Example: My wifes new system supports both Dual Core and Quad Core processors. We bought the Dual Core processor but eventually we will upgrade to the Quad Core processor. We spec'd out the memory according to what our upgrade needs will be."

That is not buying for the future in the same sense I thought you meant. It sounds like you have a fairly specific upgrade in mind, one for which you could determine with certainty what memory is supported, not a purchase based on speculation about what AMD or Intel, or motherboard manufacturers will support for future products.

3. Anyone who has purchased memory knows memory prices fluctuate, and that the relative price of faster and slower memory fluctuates as well. Those are cheaper prices than I saw in late August, which is not surprising to me. I have bought memory before.

We both agree that the faster the memory, the more over-priced it is relative to the fastest memory supported by current processors, or at the slower end of what's supported by some motherboards.

4. From my perspective it is still unwise to buy faster memory than you can use today, on speculation -- that is when your plan is based on a guess, not on what you already know to be true for an existing product or one for which the requirements have been made public ahead of time. ...particularly when there's a budget, you are buying relatively expensive memory, and there are other items where you would like to be able to spend more money, such as: a better-quality PSU, or a larger hard drive, or a perhaps a BD-ROM/DVD+/-RW drive instead of a BD-ROM drive.

5.

The amount of ram MBs support will change over time but not drastically. Most MBs support 16GB and have for a long time. There some that are starting to support 32GB.

and more of it will be needed than is already installed

I wasn't thinking about needing more memory than the motherboard will accept. I was thinking about needing more memory than originally purchased, for an operating system upgrade or memory-gobbling application.

The point is the ram you buy today will be good tomorrow even if you buy a new MB.

That all depends on the new motherboard you want to buy, and what you mean by "tomorrow". There is also a possibility that the memory available later won't be a good match for what is already installed, and it will need to be replaced, not added to. Buying extra memory today would cover your bases, but could also waste a fair amount of money, depending on what was purchased and how much prices for it drop.

My point is that the foreseeable future as far as personal computer technology goes isn't very far ahead, and purchasing significantly more expensive memory based on a pure speculation is a gamble.

An example of what would have been hard to plan for 2 years in advance: The newest Intel quad core processors. They were not backwards compatible with motherboards from two years ago, and what are the chances that memory purchased two years earlier would be a good fit, especially if there were only 2 sticks?

AMD is better about backwards compatibility, but haven't there still been times when a motherboard or memory bought two years before for an established processor family would not have been a good choice for a new processor family?

The first desktop processors with six cores will come out next year. Some people will want or need them. Do we know yet which memory available today will be a good fit for them?

Will future AMD quad cores be able to fully utilize faster memory than current ones? Probably, but what they will support has yet to be seen. Is there a possibility that to be more competative, some future AMD quad cores will support only triple-channel memory?

The next major builds aren't going to happen for 3 or 4 years

So you are looking at 2013 to have all 3 technologies on MBs in mass production.

2010 will be here soon. I mentioned upgrading "two or three years down the road", which some people might still want to do to have a couple of the things that will arrive within that span. It makes no sense quibble about this.

[A Traveller]

Thanks to everyone who replied to my questions, provided advice and helped me choose my components. For your information, I opted for RAM that is the same voltage as stated for the motherboard.