The legendary (late 2014) K80 is dropping rapidly in price. Often at around UK 300 pounds and not much more in the US in dollars amazing to see a 24 GB card at the price of a GTX 1080, more so considering the street price back then was over $4,500.
Performance isn’t so hot nowadays, both due to increased network complexity (resulting in more gradient computations) and graphics card advances (in computation, heat dissipation and power requirements) – however it does have 24 GB GDDR5 – this can never be underestimated.
Still the K80 can cost up to $1/hour on the cloud, so at this price you have to think how the cloud providers can justify this, a year ago perhaps.
Hungry power (300W) consumption, carbon footprint, slow (relatively), requires an added fan unit on the server model (the one usually sold).
With the fan component added, this is a long card, not sure how much so but certainly will be a hard fit for some workstations – some earlier workstations it may be a tight fit (card length assumptions seemed to be different then?)
Slower memory and divided into 2 x 12 GB (given this is a dual K40 GPU), this requires some extra coding to take full advantage of.
You may prefer a new GTX 1080 at the same price.
24 GB (2 x 12 GB) GDDR5
Best value used DC card (next step up P100 is in a different league pricewise)
Computational throughput isn’t trivial – can still be applied to serious work, there are plenty of K80 farms out there doing critical stuff.
Data Center supported (unlike the consumer GTX’s – another bug bear I have about Nvidias dominance in GPU’s).
If you need that RAM (and who doesn’t nowadays?) this may well be a better investment than a GTX 1080 – slower – but at least the model fits!
Bear in mind though the RAM is split between the two (K40) GPU’s.