Well it showed up yesterday, literally 20 min after I'd finished switching mobos, memtest was still running *swore*.
Anyway, the mx-4 has had time to squeeze into the grooves, mounting was easy even if the instructions we pictures that might as well have been potage-stamps
but it was just a cast of tightening opposing screws until they hit washers once the backplate was on (you'll need a long handled philips - chubby won't fit). The bad part was I received a rev.1 meaning it came with wire to attach the fan - tricky to mount - while the rev.2 ones come with plastic clips. The fan itself has rubber pads in the airflow direction, with specs similar to the viper: 600-2000 rpm, 21.2-76.8 CFM and a quoted 13-32db. Basically it spins faster than a viper and shifts less air while being as loud however the viper is a deep whirring while the coolermaster has a higher pitch* which cuts through other noises including m16s in bc2. Although this is subjective, I envisage this becoming an issue once summer hits I see myself buying a secondary viper to replace it. It is however, utterly silent below 1500rpm (where the whine appears) makinig it a decent case fan.
Still, the fan left on pwm stops giving out speed reading around 500/450rpm, which is what it drops to when idling at 30 which is impressing once you realise the bios won't drop the pwn intake fan (akasa viper) below 1050rpm (1150 once the room temp is ~ 20/21c). I've had prime running for the past 30min with the core sitting at 49c, fan at 1400 and it isn't audible over the (silent) case fans. It hits 1650 rpm with linpack and ~51c. With pwm off there's little difference, 1 degree at best in both idle and load temps suggesting the the cooler is the limitation so the extra noise isn't worth it imo.
Makes the freezer 7 look like an amateurs attempts at a cooler compared to this. Best £18 I've spent
*might just be a bad fan