1. It's good that you're starting to consider a lower TDP CPU.
BigChickenJim did a great job of reiterating why such a shift could gravely compromise your system, where heat is concerned. Given that it's an upgrade for the short term, saving a few dollars and staying within the motherboard's CPU compatibility list, sounds prudent.
2. With that motherboard, you can't over-clock whichever CPU you end up acquiring, therefore, the HD 7850 will necessitate something more powerful to be duly pushed. When I brought it up though, I was thinking of your other upgrade, where from my understanding you're going to get a new motherboard, CPU and so on. Only then, such a leap in GPU power will be justified. For now, the HD 5770 paired with a X4 840, will be a more adequate match.
A decent 500 W would handle it, but as expressed above, my understanding is that you would opt for the HD 7850 come the next upgrade, which means you would still be using your current 500 W PSU to power up your current system. The clarification came about because I wanted to assure you that a decent 500 W PSU is able to handle a single HD 7850. When I mean decent, I'm referring to a PSU that doesn't have noteworthy fluctuations where continuous power delivery is concerned. If my understanding is correct then, for your next system, you could acquire another 500 W PSU,
if you don't intend to over-clock any component and if you don't plan on adding a second GPU,
3. but make sure it's at least
80 Plus certified, so you know it's efficient enough. Read more about
80 Plus here and
here.
4. So you have 4 x 1 GB modules installed. I agree with you then, it makes more sense to get 2 x 2 GB modules and see how the system copes with 6 GB of RAM.
5. Given that you can't over-clock the CPU, I agree. You'll benefit more from +400 MHz/core, then from -400 MHz/core + 4 MB of L3 cache.
6. Yes. As
BigChickenJim points, it's likely a CPU bottle-neck. An outdated 2-core CPU running at 2.8 GHz isn't much of a gaming CPU, concerning more recent games. Personally, I was running my 2-core E8500 at 4.00 GHz, and changing from that to a stock, turbo-disabled 3570K (running at 3.4 GHz), did cause my HD 5850 to become the limiting factor in highly demanding games like Crysis 3. These two CPU's are drastically different, architecturally, but the mere availability of 2 more cores does make a significant difference. That's why the old 4-core Q6600 is still a great chip to be reckoned with, now that more applications are taking advantage of multiple cores.
7. G
raphicsDDR memory is different from DDR memory where voltage, clock speeds, bandwidth and latency are concerned, from what I understand. GDDR5 runs at a lower voltage versus DDR3. DDR3 runs at lower latencies than GDRR5, but the latter counters this otherwise performance-hindering characteristic by having a higher clock speed and, subsequently, higher bandwidth, possibilitated, among other factors by the lower heat output, thanks to being able to function at lower voltages. In short, even though GDDR5 (and GDDR4), is based on DDR3, GDDR is optimized for GPU's and can't be utilized as system memory
as is, if that's what you're inquiring. I'm guessing a different memory controller would be required, as well as different memory sockets and modules (read, more expensive) - it's not too cost-efficient, given also that increasing current RAM bandwidth isn't really necessary for the majority of computer users.
I'm afraid I can't go any further here, because my own understanding of the subject is limited. As has happened before, I briefly studied it in order to provide a substantiated explanation and even though I reckon I clarified it for the most part, I suggest you delve deeper on your own if you wish to deepen your understanding.
8. That game requires 2 GB of RAM to run, according to its recommended settings. Furthermore, every other requirement is fairly light and from what I gather, your computer shouldn't have any issue running it. Now, the fact that practically all RAM is utilized with such a light title, it's a definitive indication that your system isn't sporting a sufficient amount of RAM to handle more demanding titles, but when it comes to those, I'll make it clear that I agree with
BigChickenJim - the X2 240 is the most limiting factor.
9. A small addendum: with AMD RAM disk, you decrease the writing and reading times of applications that make use of it, because RAM is much faster than current physical drives, even SSD's. If we revert this, it can be used to explain why having a system resort to virtual memory (made available by a physical drive), instead of resorting to physical memory, slows it down significantly and may result in FPS drops, while gaming. Given the evidence you've provided thus far, this is why I don't exclude RAM as being yet another culprit. Be that as it may, I'll reaffirm that while gaming at 720p and higher, the relevance of components goes like this: GPU > CPU > RAM.
10. The PSU's themselves have a table with the values in question, generally. The voltages (V), respective amperage/current (I) and wattage/power (W). The formula to calculate wattage/power, which I employed earlier, is W = V x I. Then you have the components of the computer, for which wattage requirements are normally available on the manufacturers websites. For instance, a CPU's TDP
approximately reflects the maximum amount of power, on paper, that it will draw while running at stock conditions, fully loaded. Take your X2 240, with its TDP at 65 W. Given that nowadays CPU's draw power from the 12 V rail, you'd need:
65 = 12 x I
65 / 12 = I
5.42 ~ I
around 5.42 Amps from the 12 V rail to power that CPU at full load. You can then do the same for the GPU, add them up and if you're within the PSU specifications (consider a 5 to 10% margin of error for the results, if you're basing the values on TDP), you're good to go.
JD