I will answer the questions in order to the best of my knowledge. As I said, I am not an overclocker, and I generally leave system settings alone due to the nature of overclocking in and of itself can cause system instability and hardware damage. I am more of a software person. I can build you a good PC using factory and stock settings, and I can make sure it is stable, but I do not mess with the clock speed and I always match up memory based on ECC and latency measures. The bus speed is a different issue, as all memory will clock down automatically to the lowest clock speed of the bunch. Now that you have read my disclaimer, here we go:
1) By exchanging the stick of ram that is (possibly) running with different latency timings, you could eliminate the system slow-downs you are receiving. Since you have no obvious reason for the slow system performance, and since you upgraded the ram and it SHOULD increase the performance, it could be because the latency of the ram sticks aren't compatible. I would try removing the newest stick of ram, run the system for a couple of days and see how it performs. That may be the fix in and of itself. If you do that, you should just replace that ram with a stick that has the same latency timings as the sticks currently in your system.
2) By volatile, I mean they could go completely wacky (unstable, blue screens, page faults, overheating, hardware failure) if they are overclocked, as they seem to not be working so well together at stock speeds.
3) Running a 2.5 GB setup on this system would be a good idea, on paper. The issue here, as I mentioned above, is more than likely the difference in ram latency. Since you popped in the newer 1 GB stick, you said your system has taken a hit in performance. I am basing my theory on that info, and the fact that the ram modules are timed differently.
4) The speed of your system can be measured in multiple ways. The speed of your processor will still be the bottleneck of this system, no matter how much ram you put into it. Since you are doing some ACAD, the ram is needed to help store the info as it hits the processor, but the processor will have the biggest impact on your system's overall performance and speed.
5) 1.5 GB and 2.5 GB make little difference if you are in Windows, but the applications you are running (ACAD) will benefit from the increase. I would recommend making sure you stay at 2.5 GB, but the key here is to get the ram to play nice and run properly.
6) The timings are all based on the ram modules. You will have to read carefully when you purchase new ram to make sure it matches up with the ram currently installed on your PC.
7) Yet again, the speed performance will be bottlenecked by the Celeron's clock speed and L2 Cache (which it has little of). The ram will help with how programs run, and will allow you to run more memory-demanding programs, but your system will always be bottlenecked by the older processor.
I understand the fact that you are wanting to overclock the Celeron to make it operate faster, and I am in no way trying to dissuade you from doing so. Just because I do not overclock doesn't mean you shouldn't. I am just trying to help you get your system to a stable speed as it is, before overclocking. The fact that your system got slower after adding ram is the point I am concerned with. And if you overclock to overcome the system slowdown that the new ram caused, you are not only skirting the original issue, you are probably creating a slew of new issues as well.
If I have missed any of your points, please let me know. And if anyone has info that I have missed, feel free to add in.
Edited by Eric ~ Computer Guy, 30 November 2009 - 08:59 PM.