Its really hard to imagine these record breaking hashrate levels without ASICs in the Ethereum ecosystem.
Take Litecoin for example during the 2013-2014 Bubble.
The hashrate peaked at ~120GH/s on Jan 2014. If you were around during the Scrypt Litecoin days you would know that unlike today there were only 2 coins to mine back then. Litecoin AND Dogecoin. Dogecoin hashrate was around ~100GH/s.
However keep in mind that sometime during the end of 2013, a small era of Scrypt ASICs started emerging. So lets assume that 120GH/s was for SCRYPT GPU mining only. And another 120GH/s was being mined with the newly released 300KH/s scrypt asics.
A 7970/280X mined scrypt at 750KH/s so around ~120GHs/0.75 = ~160,000 GPUs mining. If we assume all those scrypt asics don't count then lets say ~320,000 GPUs mining.
According to etherscan.io last month a total hashrate gain of 9,104GH/s was added. Since each RX 470 ~ 28MH/s that equals to about ~325,142 GPUs. Also another 10% of that ~32,500 most likely went into the ETC hashrate growth. For simplicity I am not taking ZEC, ZCL, XMR into account.
So as much as its fun to ROI your GPU in less than 1 month, I am wondering whats going to happened when the bubble bursts. In Jan 2014, mining was VERY profitable like it is today, and in less than 6 months, it started using more electricity then profits.
However now we have most likely 10x as many miners and GPUs out there. So I can only imagine how horrific it might get when either the BTC bubble bursts, alt-coins bubble burts, ETH lowers block rewards to 3 ETH per block, ETH goes POS at end of year...
There was also DarkCoin (now known as DASH, the original X11 coin) among others - but the others didn't use a ton of GPUs.
The Gridseed ASIC didn't show up 'till early 2014 - which is what drove a ton of GPUs into X11 mining for a few weeks 'till IT overloaded, then drove most of those GPUs out of cryptocoin mining entirely
http://cryptomining-blog.com/1158-first-impressions-from-the-gridseed-5-chip-scrypt-asic/ was one of the first reviews of the original Gridseed Orb - in MAR 2014, indicating they didn't show up 'till Feb sometime.
It also took time for a significant number to deploy - Scrypt would have still; been mostly GPU mined well into March and probably most of April, when the hashrates started climbing FAST on both Litecoin AND Doge.
MOST Scrypt miiners preferred the 7870 to the 7970 or 7950 as they were a ton more COST effective, and a LOT of miners used the 7850 for the same reason.
Half or less the cost for 80% ballpark of the hashrate MATTERED.
The "average" Scrypt mining card was probably a lot closer to 600 than 750, but that would still only be about 200,000 GPUs mining Litecoin ALONE at the peak in January a month before the Gridseed Orb was introduced - and probably about the same number for DOGE at IT'S peak in Feb 2014 pre-Gridseed, so likely a half million or so TOTAL between those two and everything else of the time.
OTHER THAN Ethereum, all of the major coins like ZEC were *FLAT TO DROPPING* a hair on hashrate during January and early Febuary - in the case of ZEC, it was flat to down from a peak in NOVEMBER to today.
The crash this time around isn't going to be as bad though, as there ARE other coins around that can soak all of the hashrate while still staying profitable - as long as PRICES don't collapse in the meantime.