I'm not certain of what you're really trying to ask. Basically, CPU/RAM specifications are usually a function of the chipset more than RAM.
If I have a number of varying
processor specifications (x86, x64,
PII, P4 etc) can I accurately
calculate the memory (speed, size,
etc) that will work with this RAM?
"Accurately calculate"? Um, yes I suppose. The motherboard Chipset and usually the socket of the CPU will determine what specifications of RAM can be supported. For example, some processors are supported by chipset 'X' and 'X' does NOT support DDR3. Guess what? No DDR3 support for that CPU. That's about as simple as it gets. Some CPUs are built around RAM (remember RAMBUS?) while others focus more on what chipset can support which features they want.
Are there any 'gotchas' or can I
deduce this all from specifications
and what properties of the RAM / CPU
should I be checking?
Yes there are some BIG gotchas. People (system builders) typically get hung up on a few details: what CPU can I have - how much RAM can I hold - bus support (PCI-e x16/x8/x4?) and peripherals. The problem in looking at things in this light is that the most important factor is being left out: the chipset.
I don't care how fast a CPU is or what killer RAM you get, the chipset is the heart of the motherboard and in turn, the computer itself. Chipset determines RAM, CPU, buses, everything. So if you want to deduce from specifications of RAM & CPU, start looking at the motherboard chipset.
Another "gotcha" is RAM. RAM can be expensive to rare to find to stable/unstable. RAM is a strange beast. The faster the RAM, usually the slower the timings. If you really want to learn about how RAM works, there are lots of articles all over the web. But learning RAM timing and how the chipset works in conjunction is what really matters.
Don't get swept up in "nehalem" fever or whatever CPU is the flavor of the year. Yeah, it's a solid CPU, but if the RAM is too expensive or flaky and the chipset is 'meh' at best, it's not always worth it. DDR3 is not better simply because of speed. You have to weigh your options carefully with what you're trying to achieve. Are you building a simple computer? Workstation for development or animation/rendering or computation?
And as a last and obvious note, always read the manual before buying anything. You'll save yourself time and money.
Take the confusion out of the issue. What does Crucial or Kingston say about the memory capacity of the computer?
The manufacturers manual is a snapshot in time, it only reflects what the manufacturer tested, when the manual was being written. They are rarely updated, unless a new version of the computer / motherboard / etc comes out.
Kingston & Crucial are willing to test with newer memory chipsets, etc. So if they say your model will accept more, then it should work.
I couldn't find the board on Crucial, but Kingston states:
Standard Memory: 0 MB (Removable)
Maximum Memory: 8 GB
Expansion: 4 Sockets
CPU & ChipSet: AMD Athlon 64 (AM2) Nvidia nForce 560
AMD Athlon 64 X2 (AM2) Nvidia nForce 560
AMD Sempron (AM2) Nvidia nForce 560
Bus Architecture: PCI; PCI Express; USB
Mfgr's System P/N's: N/A
Comments MODULES MUST BE ORDERED AND INSTALLED IN PAIRS for Dual Channel mode. Kingston offers "K2" Kit part numbers for Dual Channel mode.
If 4GB is installed, the recognized memory may be reduced to 3.5GB or less (depending on system configuration and memory allocation).
Maximum configurations require 64-bit operating system.
AMD Sempron processors support DDR2-533 and DDR2-667 memory only. DDR2-800 modules are not supported with this processor.
At 1066MHz, this system supports up to two single rank modules ONLY.
DDR2-1066 is supported by AM2+ CPUs only.
Best Answer
What's given is:
Before we get the answer let's consider a few examples.
First example: We have a motherboard, that's maximum supported RAM speed is 2666MHz, and a CPU, that's maximum supported RAM speed is 2966MHz. What's gonna happen if we install a 3200MHz RAM module? The answer is motherboard will force RAM to operate at motherboard's maximum speed which is 2666MHz.
Second example: We have a motherboard that's maximum RAM speed is 3200MHz, CPU's maximum is 2400MHz. What's gonna happen if we install a ram module with crazy 3600MHz clock? The answer is motherboard will drop down RAM speed to match CPU's maximum supported clock speed which is 2400MHz. Even though you spend a couple hundreds of dollars on 3600MHz DDR4 module you will still only get 2400MHz from it, because CPU is gonna be a bottleneck for it.
And for better understanding of how all this throttling thing works, the third example: Our motherboard and CPU can work with 3200MHz memory. The first RAM module's speed is 3200, the second's is 2933, and the third one's is 2133. Whose clock speed will motherboard select? The answer is the lowest of all memory modules, which is 2133MHz. Every single module will be operating at the lowest speed of all of them. 3200, 2933 and 2133 will throttle down to 2133.
Now we can make a conclusion: Motherboard will throttle down RAM clock to the maximum CPU's supported RAM speed and/or to the lowest of all installed RAM modules.
So yes, you can install a 2666MHz module on this system. Any module that's lower than 2933MHz will be perfectly fine, even 1600MHz. But the best choice would still be 2933MHz module.