It started around June of last year. Apparently I just missed the hype. BTC has just crashed from $35, and mtgox (I think that's who it was) was hacked bringing the price down to fractions of a buck, and someone bought a massive amount of bitcoins at a ridiculously low price. Then it was all rolled back.
But I decided to try it anyhow.
Got a 6870 from newegg, and within a week picked up a 6950. That lasted a couple of months, but the heat was too much. Those two, non ref cards, crammed into a standard PC, in the beginning of summer, just didn't work well. I sold the 6950 for pretty close to what I bought it for new from newegg.
I started doing more research and found the 5000 series works a lot better than the 6000 series, although they use a bit more power and generate more heat. So I found a used reference XFX 5870 (OCd to 900mhz) on ebay (I love XFX cards.. that double lifetime warranty rocks.) What I read wasn't wrong - if I was lucky I got about 280/mh with my 6870, the 5870 got close to 400. According to what I read, if you can get 400, that's the sweet point, love it and let it go. So I did.
Shortly after I picked up another ATI 5870 ref, this one at standard 850mhz. My MB only had room for 2 (w/o risers..) so I upgraded my 600watt ps to a 750 antec, and put the 6870 in my wife's computer. It chugged away at 280, and I was getting close to 800 between the two 5870s.
This whole time I was saving my coins, waiting for the price to finally go back up. I had saved up close to 50 coins. The price finally hit $3, then $3.50, then it started to fluctuate. I sold. A week later it was $4. A week later, $5, then peaked around $6. My timing was awful, to say the least. (I've had the same experience with my limited experience in the stock market. I'm horrible at timing it.)
From that point forward I sold every coin I got as I got it, regardless of the price. Then tradehill decided to leave. I cashed out, got about 2/3's of my original investment back, minus the cost of electricity (which isn't much.. $0.0719).
The winter that wasn't started to come to an end, and the three weeks of 80 degree weather arrived. In March. (I'm on the east cost. It regularly snows in March.)
The noise and heat got to be too much, and I'd saved enough coins to buy another bare minimum rig from newegg. Put it together, and tried to get linux up and running.
And tried.
And tried some more.
Wasted a whole weekend trying to get that to work. I finally got natty working, everything installed, it saw my cards, then rebooted. All the sudden VNC went view only, regardless of what it said. This was supposed to be a headless machine, VNC had to work. At that point, I gave up on linux. I know everyone says windows requires a dummy plug or a monitor for the 2nd card (and 3rd, and 4th, and...), but I'd found a way to get windows to recognize the 2nd card w/o a dummy plug or a monitor. via tightvnc (since remote desktop causes the VC to disappear). The trick was to extend the desktop to the second card, AND make it the primary monitor. voila, 2nd desktop was there, msi afterburner saw the card, I could lower the memory clock, and best of all, with the right parms to phoenix, I get a minimum of 850 m/h between the two! Sweet!
I then moved the whole thing, headless and all, to the basement, using power line networking. I put a box fan right beside, and turned it on. Everything went as planned, I could get to it through the network, I tricked windows to showing the second card, and it was mining away. Both cards running in the lower 70s. (Right now one is at 77 because it's warming up.)
Hopefully before I run out of old windows xp licenses, I'll figure out how to get the linux on a USB key miner working.
Then I started checking out 5970s.
Ended up getting one for $364 including shipping from ebay. Hooked it up, and try as I might, I could not get more than 300 m/h total out of it. I was also having pegged CPU problems (tightvnc isn't the greatest for a single core it seems). I thought there might be too much power under the hood for that lowly semptron, so I ordered the cheapest athlon II (3 core - $75) from newegg. It arrived 3 days later. Plugged it in. No more pegged CPU problems, but still couldn't get more than 300 m/h total out of it.
So I started looking around, trying to figure out what I was doing wrong. It was more than mildly frustrating. afterburner couldn't adjust the temp of the 2nd core. my windows trick no longer worked, I'd get an error about having crossfire on.
Then I found cgminer. That's a nice miner. I told it set this memory to 300, this memory to 300, and tried out each core one at a time.
One worked fine, getting somewhere around 300m/h without much effort. The other core, however, was wildly swinging all over the place. I also noticed the HW value on cgminer was through the roof for that core, but zero on the other. Uh oh, I thought. I have a bad feeling about this. I dug into the docs for cgminer, and saw HW means hardware errors. This can't be good.
So I switched back to guiminer, using phoenix. One the first core, same experience. Somewhere around 300. On the second core, it ran good for a few seconds, then it started saying "unexpected response from API, hardware error?" Sigh. Seems I got a bad 5970.
I contact the seller and say I want to return it, one core is bad, he sold me a defective item. He told me it worked fine on his side (he used it for mining too), and was getting about 750 between the two cores. So it must have been damaged in shipment. That's funny, I thought. No signs of damage to the box, no signs of damage on the card. But whatever. He said he'll check out what it takes to initiate a claim. Long story short, he gets the money back immediately from paypal. I ship it to him, in the same box with same packing, and he refunds my money. Paypal sits on it for close to a week (argh). Yesterday I finally get the money back. Total time wasted on the 5970: 3 weeks.
Oh, and I try cgminer for a while with my dual 5870s. I average around 810 between the two, and they run hotter than I remembered. So I switched back to phoenix, and I'm getting, at minimum, 850 between them, and they run cooler. So cgminer is neat, but phoenix (through guiminer) likes my 5870s more.
My switches: -k phatk VECTORS BFI_INT WORKSIZE=384 AGGRESSION=7 FASTLOOP=false
I know everyone says higher aggression is better, but my CPU usage starts to spike at 8 with no improvement. 384 seems to be the magic worksize too. Also, I've seen some references to the last parm being FASTLOOPS, but I think it's singular.
Anyhow...
I kept checking out other 5970s, but I can't help but think in my head:
two 5870s, if played right, about $350-$375, and I get > 850m/h, and I can trick windows. One 5970, if I'm lucky, I get 750 m/h for the same price. Uses more power, and runs hotter too than either one individually. And it needs a 8 pin power connector, so my older PS's won't cut it.
I end up deciding a 5970 isn't worth it for what I'm doing. I just bought another XFX 5870, it should arrive tomorrow. I plan on running it along side my 6870, case open, horizontal, with a box fan blowing AWAY from it, to suck the heat out and force the open slots beside the cards to suck in plenty of cool air.
I've also checked out getting riser cables and building a custom open rig. Cablesaurus wants $15/pop for cables. That's $60+ shipping. For that I could get another MB, I already have memory, a CPU, and a power supply to put in it. And if bitcoin goes flop, they are not resellable. But computer hardware is, or worse case, I can donate it to needy family members who are using ancient computers.
I've learned how to make dummy plugs. I found a few DVI -> VGA connectors, and dug out my ancient electronics kit from school and got some resistors, and they work great. Yes, the windows trick works, but this is easier, and I suspect when if/when I go to more than 2 cards my windows trick won't work anymore. I've seen pictures of people using resistors straight in the DVI port, but I haven't been able to find the specs for that. That's be a lot easier than a dummy plug.
That's where I am now. I have enough coins saved up for another $100 in hardware. I'm also watching for used riser cables, with my long term idea of running 4/5870 on my machine downstairs with a second 750w PS.
Also can't wait to get out of newbie status on this board. Been reading following for almost a year, but this is only my third post. I think I know enough finally to be useful on other boards.
