Do some reading about over-clocking (will answer most of your questions). My intent is to be nice here, so please take this in the spirit intended, the questions you are asking means you shouldn't be screwing around with this until you do some research.
Typically, you don't what your CPU screaming along (unless it needs to) and then only when its important. Most of the time over-clocking isn't necessary. Most of the stuff people do does not need the CPU to be running at 1.2 Ghz rather than 700 Mhz. (it just makes the cpu hot, wears out the chip faster, might void the warranty on your PI, and causes timing throttling and lockup panic conditions. (don't do it...
If you are going to over-clock (read first everything you can about over-clocking). Then, get some good heatsinks for your PI (don't skip this step). (read about that too).
Then, do some googling to readup on what others have done and how it worked for them... you will notice that its not as simple as setting some configs and moving on... words to the wise.
I was and I am reading about overclocking (among other Linux/Raspberry information). Also checking the forum about it. Basically, my question was not about overclocking. It was about the possibility to change the CPU speed
by a simple
, it seems to me, and you do to, since you warn me about overclocking) panel-widget
. It even more surprises me, that the choices are limited to 700 and 1200 (while in the MATE-config file I read that 1000 is already the max, the turbo-choice). Therefor my question: is it really for overclocking? I also thought you have to start up with a certain CPU/RAM-setting, that it isn't something you can change "on the fly".
You say overclocking isn't necessary. Raspbian, with it's default desktop environment, is the fastest OS-combination by experience (I tried Ubuntu Mate, Raspbian with Mate desktop and with XFCE) on my Raspberry Pi 3 (class 10 SD card - will test Ubuntu from USB-stick soon). But even being the fastest, it's still quite slow, not slow continuously, but regularly slowing down and temporary freezing, even on small tasks (I try to run one program at the time). I test Evolution (the only program I found with calDAV and cardDAV support) and Firefox (the sync-option is really welcome to me, since I use different computers a lot). And just for testing Chromium-bsu, the game. Because it runs in Raspbian, but in no other combination so far. Using the openGL driver helped a little (a tip from someone on the forum) and overclocking speeded up the general speed, but didn't change the hiccups. Now I don't use the experimental driver and use the default settings for GPU and CPU.
The reason for not using the default desktop, is because of it's HUGE font and big menu's. It's made for blind people or something, the windows and menu's are ridiculously big (and behave shaky), taking up to much space. Now I removed xfce, but somehow ended up with a xfce-session. Will look-up what that means tomorrow