... You have to realize that there are a few factors at play here:
- It is not "brute force" at play here, but rather the need for more resources to perform more advanced functions (HTML5, advanced CSS, WebGL, hardware accelerated graphics, to name a few)
- Pale Moon 3.6.32 will not be able to render pages correctly anymore that use current coding standards, and you will have issues using an increasing number of websites.
- Performance of Pale Moon 15 is significantly better than pale Moon 3.6 -- unless your system is indeed so low on resources that it will start to swap to disk. But that situation is not a problem with the browser, all things considered.
- PCs from the last decade or so have enough memory and other resources to run Pale Moon 15 comfortably.
- I agree that "buy new hardware" is often used as an easy excuse to push inefficient software, but in that case you are normally looking at hardware that is, by all means, not seriously outdated yet.
- Pale Moon may simply not be a good choice for you since it does not necessarily aim to be a lightweight browser. It aims to be efficient; efficiency regularly means using more resources to do things in an optimal way.
- If you are looking at memory use including the plugin container, then you are also looking at what Flash is using, and Flash can be a real memory hog (and that is out of my hands entirely).
If your computer is of such an age that the currently maintained version of Pale Moon doesn't run properly on it, then you are better off finding a lightweight, maintained browser instead of running an unmaintained and outdated Pale Moon version. Trying to "force the issue" on Pale Moon will have you take security risks when browsing, if nothing else. Pale Moon 2.0.0.20 (the only 2.x one published) is even lighter on resources, but has even more severe issues.
The world moves forward; buying new hardware on occasion is part of progress. If you don't have a budget for a current PC, get a second-hand one at a bargain price.
That being said, the specs of the computer listed:
Processor Intel Atom N270 / 1.6 GHz
Memory 1.0 GB ( 512.0 MB soldered) / 1.5 GB (max)
Hard Drive 120.0 GB
Should definitely suffice for running Pale Moon 15 comfortably. Since you are dealing with an Intel GMA in that machine, you DO want to disable hardware acceleration if you run v15. This will also reduce memory use. Another thing you want to disable most likely is smooth scrolling - it is relatively expensive in terms of CPU and your netbook will simply not be well-suited enough to use it.
