I bought a Radeon HD 6870 and 7950 to help mine altcoins, thinking it would all pay off in two months.
No excitement here, these are slaves, workers, brought in to do the work my trusty olde GTX470 can’t do by itself. As such, I only took pictures of the Radeon HD 6870, but not the 7950. Well… it’s dead now. But I’m getting ahead of myself.
The first thing I noticed about the 7950 was either the cooler sucked (Sapphire Dual-X), or the chip puts out way more heat than my GTX470. Ran a bit of Metro 2033 on the thing just to satisfy my friend, didn’t feel noticeably smoother than on my GTX470 unfortunately. Also ran Crysis 2 on DX11. The added oomph from the 7950 wasn’t enough to make Crysis 2 as smooth as DX9 (on my GTX470). Overall, gaming wise, I hadn’t gone anywhere. Not that I needed extra performance in games – I hardly play games anymore.
Mining was a good upgrade over my overclocked GTX470. The Radeon HD 6870 didn’t want to work with the integrated Radeon HD 4250 in my second computer, but once I told it it was the only card for me, it set to work making LTC/FTC/CNC at 300kH/s (this is at high intensity). The Radeon HD 7950 managed to score the same amount at low intensity settings in GUIminer-scrypt (preset: 7950 low usage) but at high intensity it could pump out 450kH/s.
This made the desktop incredibly laggy, even if it was driving only one monitor, both monitors would be laggy. Seems to be a Windows issue, no wonder so many headless mining rigs run Linux. So I kept all the monitors on my GTX470 instead, and enjoyed smooth desktop operation while the 7950 cranked away.
All in all, 450kH/s+300kH/s+150kH/s is not an impressive show, when I bought the two cards, I had banked on the 6870 producing 350kH/s, and the 7950 to produce ~650kH/s. Turns out these were only peak figures achieved by people with watercooling loops.
Then I found that Powertune was throttling the 7950 down to 64% every now and then. WTF? When I buy a card with a custom cooler, I expect it be able to run at stock clocks without throttling, no matter the workload! So I raised the limit, and overclocked it, but I found that the overclock made Powertune throttle the GPU down to 64%… again. I figured the 100% of 925MHz was better than an intermittent 64% of 1100MHz… so I left it all at stock clocks, but kept the Powertune at +20%. OK, it’s now at 100% and not throttling – but I’m only getting 560kH/s, max. The Litecoin wiki said I’d get 600! (spent some time with thread-concurrency at 21712-24000, nothing got me up to 600 on stock clocks.
Nevertheless I had other concerns. It was getting really fucking hot, the GPU was reaching 83C. and loud. Freaking loud. The 6870 was working hard, and I couldn’t hear it over the background noise coming in from the open window. The 7950 made my PC sound like a blade server, and the sheer heat scared me enough to keep the case open, and the window to my room open. With the case closed, the heat from the 7950 made my Phenom II X6 just as hot as if it had been working at 100% too. I decided to leave the 7950 alone at 560kH/s and not overclock it.
I put up with this racket for two days, helped immensely by a pair of green foam earplugs and copious amounts of cold tap water on my body. In the end, I decided to give the computer a rest – I was hearing a rattling fan somewhere in there. Killed the miners (I got one block of BTB! yay) and let it idle at the desktop for a while. Then I shut the system down.
Ah, some peace and quiet. The Corsair Graphite 600T is making cracking noises as it sheds the heat, damn that was some workout. The CPU’s heatsink, despite it idling all the time, is hot. The heatplate on the 7950 burnt my finger. The GTX470 is doing just fine despite being just below the 7950 and running cudaminer (I don’t know how but Gelid’s Icy Vision custom heatsink is an incredibly good performer). Really, such peace and quiet. XFX’s 6870 is working in the other computer, reliably, making a loud whooshing sound but nothing really grating. OK, it’s time to get back to work.
I press the button, and my LED fans flash on for an instant, and quickly die. I smell something. Fuck. was that my mainboard? was that…. anything? I press again and again, the computer refuses to turn on, seems like the PSU’s short circuit protection is working. I pull out the Radeon HD 7950 and the computer boots.
God damn. So much for high quality Black Diamond chokes. So much for the Dual-X cooler. So much for Powertune. So much for mining!
1. Graphic cards should be seen and not heard.
2. Slow, steady and silent is actually preferable to fast, hot and raucous (does this mean I should mine LTC instead of the more profitable FTC/CNC?)
3. Sapphire’s Dual-X cooler isn’t all that. Shitty hardware review sites like techpowerup.com say that the cooler keeps the GPU at 63C while being silent, without mentioning that this is all because Powertune is silently throttling it in the background. Although Sapphire’s Dual-X heatsink is “custom”, the aftermarket Gelid Icy Vision dissipates the same amount of heat silently, without any fuss. I’m sure my GTX470 can put out more heat.
4. Most importantly: mining is for suckers. Buying hardware just for mining is for real suckers.
The 7950 is going back for a refund. It wasn’t perceptibly faster than my GTX470 anyway, despite what Anandtech bench may say.