Prior to writing this, my experience with Yosemite has been mostly positive other than the egregious usage of Helvetica, which was easily remedied. 

However, on my work MacBook Pro Retina early 2013 (15 incher/i7) has been borked since my update recently to 10.10.2. My wifi speeds dropped abysmally, with transfers topping out at 21k a second, usually much lower. 

After trying a boat load of voodoo tricks, such as deleting plists and saw a reddit post recommending killing discoveryd (not the best idea), and I still may yet try reinstalling mDNSResponder. That said, here’s the fix.

The quick fix

However so far there is a fix, and anyone who remembers OS 7 through OS 9 will remember the magic of Zapping the PRAM and its miracle working to make bad SCSI chain start magically working.

  1. Shutdown or reboot your Mac
  2. Hold Option, Command (⌘), P, and R and power up the Mac (or hold while rebooting), this has to be done before the white screen appears.
  3. Hold until you hear the boot chime for a second time.

Notably, the problem may creep back and you’ll have to do this again. I managed to last a week before I had to rezap the PRAM. This hopefully will get you by until Apple manages to fix its networking woes.

A little history…

So what is the PRAM? Back in the “classic days” of OS 7, OS 8 and OS 9, Mac OS stashed important OS settings in the first meg or so of memory, referred to as the Parameter RAM. In early Macs, these settings were stored by battery by battery so they were not lost when powered down.

Later Macs switched to NVRAM (non-volatile RAM), which is the same concept as PRAM, settings that are stored by battery (Screen resolution, network ports available, Speaker volume, startup disk selection, Recent kernel panic information, if any) outside of the computer’s disk storage.  The term PRAM carries over as legacy as well as the key commands. The term PRAM is still used interchangeably even if not technically correct.

/Edit: 5/30/14:

OS X 10.10.4 reverted back to mDNSresponder. Goodbye discoveryd, upgrading to 10.10.4 should solve any major networking issues with Bonjour and OS X.