Make sure to read everything, there's some questions at the end
About a month ago I went ahead and got a HD 7850 2GB from Sapphire, second hand, I was looking to upgrade my R7 250.
All was well and good, it was running a bit hot, but I didn't pay much attention to it (wouldn't exceed 76-77 degrees, but I had to undervolt to keep it from becoming a jet engine), performance was good too, superior to the 250's, but I thought it had had its bios re-flashed, because the picture on the bios database had a different cooler than mine, while I did later learn pictures there aren't 100% representative of what the card actually looks like, it did have its bios re-flashed, but I'm getting ahead of myself.
And so, performance in some games was kinda poor, games like Borderlands 2, still playable, but absolutely abysmal frame times and wouldn't get past 45-50fps max, same story with Serious Sam 3: Fusion, while others did run well, I didn't know how poor they ran until I got a replacement, but I'm getting ahead of myself again.
Fast forward to 3 days ago, when I was getting seemingly power delivery issues. The card looked good both idle and in-game, no artifacts, however under stress the driver would crash leaving behind lines of the same looking gradient repeated, something I know is caused by not enough voltage, because I had an unstable undervolt that behaved just like that.
Anyway, yesterday I took the card back to the guy I got it from, and he was friendly enough to help me figure out the issue. I was hoping it was my power supply that had the problem, because it's still in warranty, but it did the same "unstable undervolt" crash on him, too. We tried re-flashing the bios, thinking this is what may have been causing it, and THIS is where I learned the card had had its bios re-flashed by somebody else, and really badly at that too because it couldn't be re-flashed again, not even showing anything in atiflash.
Meanwhile, I left that card at the guy and he was kind enough to give me another HD 7850 he had, this time from MSI, but only 1GB in size, I took it kinda reluctantly thinking it would impact my performance because it had half the buffer, but when I got home I was pleasantly surprised that not only did it run 10 degrees cooler than the Sapphire, with a slower fan profile, too, but it was also running so much better, now I'm able to get 70+fps (can't tell exactly how much above that, I've locked the framerate) in both Borderlands 2, and Serious Sam 3: Fusion.
Now there are also some questions to be had after all this.
1. Are old Sapphire cards, from about that time really bad? Are they still this bad? My R7 250 is a Sapphire and I haven't had any issues with it in the past 3 years.
2. Could the poor performance in the Sapphire card have been caused by the poorly flashed bios?
TL;DR: I bought a sapphire HD 7850 that went bad shortly after, got it replaced with a 1GB version from MSI which somehow performs vastly better.