I believe Trixx requires both a GUI and MS Windows so it's not useful to me unfortunately, thanks for the tip anyway.


WOW! 1.6V!  That's a 47% overvolt!  I'll bet whoever did that would be able to beat my 461.1 MH/s personal best 5850 rate (stability unknown.  I ran it for 3 hours and it crashed exactly when I started up the other card).

Man... 1.6V.

I'm at 300MHz.  I meant that decreasing to 180MHz and dropping the worksize from 256 to 128 seems to do me no good no matter what my other settings are (Sapphire HD5850 Xtreme).


No, I originally tried to underclock/undervolt everything as sensibly as I could but ended up but couldn't boot at all and ended up having to reset the BIOS/CMOS/whatever.  Since then I've just touched the CPU and RAM setting and have been afraid to touch any of the dozens of other settings for breaking my board (I have no experience with this kind of thing).  If you can give me a little more detail about this I'll try it and see if it helps.


Yep.  You can safely assume that I'm not running any 'services' at all.  Got a daemon or two running but powertop thinks they're all benign.  Linux is much easier to configure with respect to power consumption than the BIOS because of all the helper tools and documentation so assume that the OS related stuff is largely done.

I have no idea but I've been told that my chip is very efficient so that must help a lot.

I think the bulk of my power saving may come from running the cards at low voltages.  At stock voltages I was using quite a bit more than 400W but with a 0.1V undervolt (1.0875V -> 0.9875V) on both cards 304W is my average draw.  Unfortunately, I had to lower the clocks on the cores to get stability back; 975MHz -> 845MHz and 1020MHz -> 895MHz respectively.  I was running at 850 and 895 but my 850 card crashed after 36 hours.  What voltages are your cards at?

I haven't disabled USB in the BIOS despite the fact that I have no USB in use.  I have no SATA, sound, firewire in use either but I left them on in the BIOS because I didn't see a difference in the power draw between enabling them and disabling them (I only checked power consumption in the BIOS though).  All I changed in the BIOS was the CPU voltage, CPU and RAM clocks, and I set the motherboard to be always switched on.  Given all the people talking about tweaking the BIOS I think I'm going to have to go back and have a proper look at this.

I also keep thinking about the possibility of doing away with the hard-drive but there's a fair bit of work involved in unhooking this for what amounts to 83p (1.34 USD) per month.

That's interesting, I may well investigate this now that I have my power meter.  I have no GUI or sliders and am only changing my voltage by modifying the profile file with a text editor.


Catalyst 11.6 does allow me to go past 900 but this might be peculiar to my card.  I'm using Catalyst 11.4 because it seems to be quite a bit faster for me than Catalyst 11.6.

You are wise to show such restraint.  I took my good card up to 1.3V on air cooling in an attempt to find it's maximum and learnt 3 interesting things.
1) Catalyst 11.6 doesn't allow you to go beyond 1.3V.
2) My card is actually able to reach higher clocks at 1.25V than at 1.3V (this is because the cards are less stable at higher temperatures).
3) My Sapphire HD5850 Xtreme will take 1.3V without exploding.  If only I had my power meter back then.

Just for your information, I ran at 1.3V for only 20 mins or so and half of that time I wasn't running mining software.  I did run at 1.25V for 3 hours continuously mining at 1110MHz (461.1 MH/s) and maintained a temperature of 56*C with aftermarket air cooling.  The card showed no signs of distress; there were no funny smells.  Since then I've bought the voltage down and it runs just as it did before testing.

Nice.  How have you accounted for the proportion of the base wattage which is going to the cards in idle mode?

I found that the maximum overclock is pretty much a hard line at lower voltages.  My cards are at 850MHz and 895MHz.  If I clock either of them up by 5 MHz they crash instantly (tried twice with both).  They've been running at 850MHz and 895MHz with no problems for 36 hours now.  I experienced the same thing at 1.0125V on my slower card where 900MHz was very stable and 905MHz always crashed instantly.  I may have to start moving by 1 MHz intervals.

At higher voltages I get all sorts of nonsense.  Sometimes my good card will run fine at 1035MHz for 36 hours.  Sometimes it will crash when I try to run it at 1025MHz.  Sometimes I'll get kernel errors.  All at about 55*C!  I just don't understand it.

Note: My cards are very much dedicated to mining and I don't think any other program is trying to use the cards.  In particular, when I plug a monitor into a card I get no signal.  I've seen some people trying to run a GUI at the same time which can seriously affect stability.

Yeah, 5 blocks for 200khps over a few months.  However, even with the low difficulty and low power consumption, 150 of those BTC were barely profitable and the other 100 I generated at a loss.  Bitcoins were not highly valued back then.

I took a chance (bought 1500 BTC back when all the bids and asks were multiples of 100 BTC) and got lucky!

I was excited when people started taking more interest.  knightmb decided to set up a mining farm and everyone thought he was nuts!  Eventually there were problems with the main exchange (paypal scams) and someone started a new exchange which was supposed to do everything properly and professionally (mt gox  ).

Ah! memory lane.

Thanks for this, very helpful!  I'm assuming that you are not putting 10.88V through your cards but, rather, 1.088V.  Also, are you really able to put 1.118V through the card?  I've been working on the assumption (I make a lot of those) that the cards operate on multiples of 0.0125V so I would expect 1.1125V or 1.125V.  Given that 1.118V is closer to 1.1125V than 1.125V I'd guess that the driver is rounding your figure down and the card is really on 1.1125V.  Any thoughts on this?

If I find the time I'll post some values for higher overclocks and overvolts (I can only go up to about 1140MHz and am limited to 1.3V but it could be helpful).  I've not done this because it would mean installing Catalyst 11.6 and rebooting the system (11.4 doesn't allow overvolting or overclocking past 900MHz on my cards as far as I know).

One of the two cores on my Intel Atom D510 (the other core was F@H).  I got 250.01 BTC with this .

I think a threat of legal action due to copyright infringement is a greater crime than copyright infringement itself.  The damage caused my such threat is quite real for a start (psycological) and if it were levelled against someone who might feel intimidated then I would be appauled in the same way that would cause others to call for banning the poster and censoring the material.

Fortunately, Vladimir seems to be more 'annoyed and amused' than 'intimidated and upset'.

When we are talking about large-scale intentional copyright infringement then a threat of legal action is distasteful to me but understandable and people involved in such operations should know to take steps to hide/protect themselves.  However, threatening people just sharing images they found on a website is despicable.

I hope that this 'threat' was really a kindly-worded polite request by the artist that their name be included near the image (very much acceptable in my opinion).  If they mentioned copyright law at any point then my reply would be, and always has been, "f*** off".

Also, I think the term is 'Nazi', not 'Copyright Nazi' just as it is 'Pirate' not 'Copyright Pirate'.  Don't worry, English is a tricky language.

I'm still not sure whether this 'disconnection' is something to do with the miner or the card.  Is the driver crashing?  Do you have another program that will stress the card which you can try running after a 'disconnection' to verify that the card is perfectly happy?  Could you try different mining software for the second card?

Are you pool mining?  If so, are you sure that you are not just disconnecting from the server?  Perhaps try a different server or, better yet, solo mining, and see if the 'connection' problems persist.

Could be.  My main computer consists of an intel chip and board and consumes about 55W total at 100% system load.  I'd expect to lose about 70-80 MH/s by taking both cards from 1.075V to 1V so and for your Mh/J to increase significantly but if you are profitable at 0.3 Mh/J then surely the 70-80 MH/s is worth quite a lot more than the power you will save.

My personal motivation for undervolting is to decrease noise levels and I know I would be more profitable at stock voltage.

You are doing well to be profitable at 0.3 Mh/J.  I'd be at a loss below 0.5 MH/J, but I guess that's just power costs.  Ah well, I can't have all the advantages I guess.

I'm not in a position to test power consumption increases right now (otherwise I'd have done that from the beginning).  I'm just calculating based on my limited knowledge of electricity and how cards work.

For the doubling, I'm noting that an increases in voltage from 1.0875V to 1.25V is a 15% increase in voltage which implies a 32% increase in power.  Overclocking from 725 MHz to 1110 MHz is a 53% increase.  Overall this is more than a 100% increase.

I have some possibly faulty assumptions and if you have knowledge to allow me to dodge these then let me know.

1) Increasing temperature increases electrical resistance which decreases current and therefore decreases power.  I'm assuming that the temperature of the GPU is kept constant as voltage and clock rate are increased but this assumption isn't too bad because many people ramp up the cooling when they overclock/overvolt.

2) I'm assuming that the core clock affects the power consumption linearly but this could easily be way off.

While Tom's Hardware gives some good stats it would be unwise to look at the max performance power consumption and use that to tell if you are safe for overclocked mining.  It's quite possible that the 'max performance' concerns core clocks which are significantly less than 1110 MHz.  Mining is inherently more stable than gaming or desktop graphics so you can push the clock rate quite a lot higher.

Overall, there are many factors to consider and, as my earlier comments show, it is very hard to make accurate predictions of power consumption using theory alone.  If you want to be safe then I can only recommend getting a power meter and ensuring that you are not stressing your PSU.  Honestly though, I wouldn't be worried about overclocking and would wager good money that a typical non-dedicated miner with 2x5850s at stock voltage, no matter what the clock rate, could possibly worry a 650W PSU.  If you overvolt too then you might run into problems.  I stress 'might' this time because people didn't pick up on it in my original post.

I know practically nothing about overclocking the 5870s although I did see a screenshot of someone using Windows who had their 5870 up to 1.35V and 1135 MHz so they were able to break my current 1.3V barrier.  Not knowing makes it a gamble, particularly with Linux as Sapphire don't seem to be aware that Linux exists.

If you can unlock the shaders then a 6950 looks like a good plan.  Unlocked it might be competition for a 5870 (the 5870s are incredible miners).  I still can't say anything about your ability to overclock or overvolt but if you're using Windows then the risk is small.

Also, if you are looking for energy efficiency then 430 MH/s might be a bit much for an unlocked 6950.  I see from the linked page that this is achieved by taking the card to 1.275V which is a pretty serious overvolt.  Remember that power increases quadratically with voltage and linearly with clock rate so a 20% overvolt on both should give you about a 73% power consumption increase (of the gpu - not necessarily the whole card).

I agree, if well designed a case can actually help to keep your system cool.  With just 2 graphics cards you might just about manage with a well designed case and you could put in sound insulation then.  With heavier mining I think the majority of the people posting on the pictures thread have the right idea and are cooling their cards much more efficiently than could be arranged in a case.

Just for fun I decided to put all of my fans to maximum and leave them for 30 mins with the Window and door wide open.  My temps plummeted to 44*C and 36*C respectively .

My apologies, I didn't do any calculations and was just impressed with the large power reduction I experienced with my 0.1V undervolt.  I didn't express myself well and just wanted to get across my impression that I wouldn't be overvolting to any great degree if I wasn't fully confident that the PSU could take it.

Just as an example of an overclock I performed myself: Overclocking from 1.0875V@725MHz to 1.25V@1110MHz should approximately double your power consumption.

Without some testing I couldn't say for sure if a 650W PSU could handle any dual 5850 mining rig and I would guess that some dual 5850 rigs will require more than 650W.  However, it seems very unlikely than a 0.1V overvolt could worry such a PSU even with a heavy base system power draw.

You are getting much lower base-system power consumption than I am (I'm at 111W with both cards idle).  I'm sure the HDD is one culprit but it's not enough on it's own to explain this gap.  I'm also only running 1GB of RAM.  I can't even pretent to compete with this, well played.  My high MH/J is probably partly due to the efficiency of the 5850s and partly because my cards are running at a much lower voltage (0.9875V).

My PSU is certainly getting fresh air (not a problem with a rig mounted on a board).

I just discovered that increasing all the fans to maximum increases the load by 7W total right away but if I leave the system running for 15 minutes then the power consumption slowly drops until eventually I'm actually saving 6W (so down to 298W total)!  It seems the temperature of the gpus has a pretty serious effect on power consumption.  Unfortunately I cannot make much use of this because the miner is too loud to run like this 24-7.  It's a shame, 2.43 MH/J would have been awesome.

Undervolting my cards and maxing the fans really did a number on my temps: 44*C and 36*C respectively (the 44*C is sucking in warm air from the other card).  At 36*C and churning out 371.6 MH/s you might guess my 5850 was under water .

Private communication with the original builders of my rig, BlightyCoin, revealed that some Sapphire 5850 Xtremes can be overvolted to 1.3V on Linux with Catalyst 11.6 and AMDOverdriveCtrl but some will not go beyond 1.0875V.  Given that my cards do go beyond and their cards do not and because I believe I ordered one of the first rigs they assembled, I think that newer BIOSes will limit your overclocking potential in Linux.  I'd be very worried about overclocking/overvolting limits in your position as they were the greatest obstacle to configuring my rig.

If you are using Windows then you have Trixx but I hear there are a number of annoying limitations with this too so beware.

All I can advise is to read everything you can find on the subject, buying the card is almost certainly going to be a gamble but you can atleast get the odds in your favour.

Also, if you cannot overclock you can always undervolt instead so that the rig isn't completely useless but I guess this is little compensation.  My good card is undervolted by 0.1V and it still clocks 170MHz above stock so the untapped potential could be huge.

Best of luck!

Given that coolers on cards almost always suck in air from the front and blow it out the sides it would be better to blow cool air between the air than try to suck warm air out.  If you check out The Koolio's pictures you'll see that he is of a similar opinion http://forum.bitcoin.org/index.php?topic=7216.msg324784#msg324784.

My first card is always about 15-20*C warmer than my second because it is sucking in air which is being heated up by the back of the second card.  I have no chassie fan and my coolers are a full 3-pci slots wide (meaning little space between the two cards) so the effect is significant.  I've recently installed a second CPU-sized fan blowing air onto the back of my first card (of course, at a low speed to keep noise down) and this has helped significantly.  My temps are now 59*C and 47*C respectively (with my window closed).  Perhaps best would be to have a chassie fan on the top (two if your cooler has two fans) and a cpu fan blowing the back of the hot card.  With all the fans turned right down the cooling should still be effective and you can reduce the speed of your cards fans a little more (if they are still audible).

I suppose this could be a feature of the mining software.  I know hashkill has an option to stop when the GPU reaches a certain temperature.  If you're comfortable at 70*C then you could investigate and possible increase this limit.

Myself, I found that at high voltages and very high clock rates that my cards will start running perfectly fine and then cut out when they reach a certain temperature.  However, this was usually within 2-3 minutes, the exact temperature would vary slightly, and the driver would freeze (which I'm guessing isn't happening to you given that you said 'disconnect' rather than 'freeze' or 'crash').