I currently have an i7 3770k running at 4.8 GHz at 1.275v, with a Cooler Master Hyper 212 EVO CPU cooler.

Under full load it sits at about 70° C (100% CPU accross all 4 cores), but under tests like Prime95 it can get quite a bit warmer.

I'd like to overclock a little more, as from what I've seen the overclock / voltage I've got makes it look like I must have a good CPU - but I can't really push it any higher on it's current cooling.

I've seen Corsair H100's for as little as £60 refurbished from eBuyer.

Question is - is it worth it? Am I going to be able to get any more usable clockspeed out of my CPU?

I don't mind the cost so much, it's the hassle of taking the motherboard out to fit the backplate! (my case has a backplate hole by the motherboard, but it's in the wrong place!)

I bought the H100 and 4 Arctic F12 fans to use in Push/Pull config with the radiator.
My CPU is the AMD Phenom 1090T 6 cores and is overclocked to 4.5GHz with 1.6v (1.7v at load) stock voltage is 1.45v with a clock of 3.2GHz

The H100 on its lowest quiet setting on the pump keeps my idle temp the same as my ambient +/- 1C
At full 100% load with Prime95 x64 I get a max of 44-46C after a good few hours.

I've not had any other cooler but the stock AMD couldn't handle over 3.6GHz without hitting the thermal wall 70C+ so the H100 has really lowered the temp and allowed me to overclock 1.£GHz more than its stock clocks and with an increase of 0.2v or so.

E: Also (I'm sure you probably know) but when overclocking especially beyond 4-5GHz be sure to run Prime95 for at least 12 hours to be sure its 100% stable. If it crashes/bsod running prime95 it is not stable, whether it never crashes when gaming etc if it does with prime then its not a stable OC

For what could you possibly need that much CPU performance in the first place?

Quote from Forbin :

For what could you possibly need that much CPU performance in the first place?

I'm a geek, I like my PC fast. Even if I didn't need the CPU power, I enjoy getting the most out of my CPU - I didn't have the opportunity to overclock much with my previous PC's (poor stepping Xeon, my generation Phenom didn't overclock well) and I'd forgotten what it's like to have a properly overclocked PC (my AMD 3700+ ran at 40% OC)

However, my PC is always at full load (password cracking - I zipped up all my files and then lost the password!) but also it's used for photo / video editing and for lots of Uni stuff. Basically, I'm a CPU whore.

Quote from Jakg :

I'm a geek, I like my PC fast. Even if I didn't need the CPU power, I enjoy getting the most out of my CPU

I'm also a geek, but as an engineer, this makes me facepalm. Assuming you weren't trying to crack your .zip, you're just generating a lot of heat and spending a fair amount of money dealing with that heat for nothing.

Quote from Jakg :

(password cracking - I zipped up all my files and then lost the password!)

http://xkcd.com/936/

Quote from Jakg :

However, my PC is always at full load (password cracking - I zipped up all my files and then lost the password!)

Looked into any form of GPU-accelerated search?

GPU's have a lot more processing power for the likes of bruteforce password cracking.

Quote from amp88 :

Looked into any form of GPU-accelerated search?

Quote from DavidTiger :

GPU's have a lot more processing power for the likes of bruteforce password cracking.

No

To make you cry even more - the software I'm using (rarcarck - it's a .7z file) is Linux only so it's running in an Ubuntu VM!

I really should just write my own at some point but... effort

I can't wait for that 7z to get unlocked. I've seen the file list of it.

Edit: I actually still have it somewhere. :P

Quote from Jakg :

To make you cry even more - the software I'm using (rarcarck - it's a .7z file) is Linux only so it's running in an Ubuntu VM!

This rarcrack by any chance? This thingie is a nice POSIX + C exercise but not an actual archive cracker cRARk is a much better CUDA/OpenCL aware tool which runs even on Windows.

Quote from MadCatX :

This rarcrack by any chance? This thingie is a nice POSIX + C exercise but not an actual archive cracker cRARk is a much better CUDA/OpenCL aware tool which runs even on Windows.

Ooooo that looks good, I'll give it a go

Quote from MadCatX :

This rarcrack by any chance? This thingie is a nice POSIX + C exercise but not an actual archive cracker cRARk is a much better CUDA/OpenCL aware tool which runs even on Windows.

I've been trying this all day, despite saying it does OpenCL it just says my card doesn't do CUDA and then goes to the CPU and only runs on one core very slowly.

It's also totally failed to find the very simple passwords on the last 3 files I gave it ("test", "ab" & "abc") so I can't really trust it either :/

Shame as it looked good!

(rarcrack does ~3200 passwords/second inside Ubuntu running within VMWare, using all 4 cores at 4.8 GHz)

you realize that 5 year old pics of ex girlfriends probably qualify as rather illegal for someone your age?

Maybe you just set the "password.def" file wrong? If I put this into the file:

it brute-forces over a mixed-case strings containing numbers of any length. My sorry-ass 3.5 years old laptop with a C2D and 9800M GTS crunches through over 800 p/s. I only tested the 3.43 Linux version, but it picks the CUDA up fine. By the time I finished writing this it successfully cracked a 4 chars long password in under 7 minutes averaging 921 p/s.

EDIT:

Quote from Shotglass :

you realize that 5 year old pics of ex girlfriends probably qualify as rather illegal for someone your age?

If I had such files on my hard drive, I'd definitely be using be the joint power of all computers I have access to to get the password

EDIT2:
Just for comparison, running this

takes over 32 secs on the same machine. This is essentially what the rarcrack does (with different passwords of course) and on my lappy it makes it about 15 times slower (if it used both cores).