I recently got a box of 7970s that were supposed to be in perfect shape. Out of 5 cards, only 2 were able to complete the Uningine Valley test twice in a row. And I'm afraid that was the last straw. The AMD Tahiti cards are the last ones with full driver and EFI support. Lots of people want them, and when they work, they work pretty well.
However, some time back I noticed that although they represented 20-25% of our sales, they were easily 50-60% of our returns. I have far more dead 7970s than I do dead Nvidia Kepler cards. Getting stuck with dead cards is a bad deal for us. As it was, we had to double the stress tests for the cards to catch more bad ones before they shipped to our customers. But having 60% failures in one box was too much.
We may occasionally offer some R9 280X cards when we find them in reasonable shape, but I can't justify the time and expense of testing cards that fail so often. The older 7950 and 7970 cards will no longer be stocked by us unless I stumble upon some really choice ones.
We will be happy to flash them for our customers, but suggest that when you buy them used (no new ones made in years, so no choice really) that you test them thoroughly before sending them for flashing. The standard failure mode for these cards is either screen going black while machine keeps running, or entire Mac Pro shutting off due to excessive power draw. Run that Uningine Valley test on "Extreme HD" at least twice in a row to weed out the bad ones.
Many of these cards spent their early lives in Bitcoin setups, running at 100% 24/7 for months on end. And, as we all know, AMD cards are not the best in the performance/watt area, this means more electricity gets used heating up the card versus getting work done. (Like comparing an old incandescent bulb to a new LED one.)
We have a few "oddball" ones that we will be listing soon, a couple single DP ones, and a couple where the HDMI port only works in certain circumstances, etc. These will be pretty inexpensive, but they will be the last.
If someone knows of a source for some good, non-thrashed 7970s I'd like to know.