http://downloadmoreram.com/

cpu-z is all you need for what you want to know

Aida 64, its better to buy 2x8 then having 4 sticks. You need to check what your motherboard will work with

The Crucial scanner (if you trust running it from the Crucial website) will scan your pc and list all you need to know - it will select compatible RAM for you when it reads your system.

In Linux:

$ cat /proc/meminfo
$ free -m
$ free -g
$ free -k
$ top
$ dmidecode --type memory

GNU/Linux, mind you.

Yes, indeed =]

Genuinely interested: What are you doing with your machine that 8GB of RAM is not enough? Big VMs? Heavy Video/Image editing/rendering?

I've been on 2 on my desktop for years and it's getting annoying, question is should I get 8 or 16. I intend to just get a new PC alltogether and do GPU passthrough (current one is a shitty HP prebuilt from 2008).

multiple displays, thus multiple programs which have some impact too maybe?

Normal programs really do not require that much RAM nowadays. I'm on my laptop with 4 gigs available right now, 20 tabs in firefox, 5 different pdfs, a few terminals and I'm well under 2 gigs (according to htop). Libreoffice would require .5 gigs (maybe a bit more for really big calc sheets or calc sheets + writer docs etc.), and that's pretty much everything covered that normies like us do on a computer. When I was writing my Bachelor thesis I had like 30 pdfs open at times, which consumed maybe 300-400 megs.

How one makes effective use of 8 gigs is beyond me.

He's just spending his mom's money on things he sort of wants. He "needs" the ice cream he just saw at the counter.

Equally same programs, I guess maybe then for some 3d/video or something similar artist :)

Building Chromium, and I guess Firefox is similar in this case, requires at least 8 GB or RAM, but that's not something your average Joe does every day, if at all.

Try: http://masm32.com/board/index.php?topic=5964.0

Take it out and look on the side of it!