Topic: Maximising MH/J (Read 4687 times)

I meant that I configure my cards to not drive a display at the same time as mining.  If I plug a monitor into one of my cards I get "no-signal", rather than some console or GUI mode.  I drive and monitor the cards by ssh.  This is the logical conclusion to tricks such as 'disabling desktop effects' or 'disabling Flash hardware acceleration'.  The tricky bit is still being able to modify voltage and clocks (aticonfig is not very sophisticated, makes bad assumptions, and is closed source) but it's at least possible with my cards.  I'd go into more detail but it's very much off topic for this thread.  I have no idea how to do this in Windows I'm afraid.

You can shut off alot of the window effects in Linux each of which take some GPU time to handle. Transparency is particularly nasty.

What do you mean by this?

Yes, I was getting around 402 Mh/s (970 MHz) on one card and 423 Mh/s (1020 MHz) on the other completely stable.  Undervolting by 0.1V took me down to 351 Mh/s (845 MHz) and 372 Mh/s (895 MHz) respectively and I'm still testing for stability so they may drop a little more (currently they've been running like this for over 48 hours).  The bulk of this hashing power comes from high clock rates and although I believe I have lucky cards I'm fairly sure this also has something to do with removing the GUI.  If you are using Linux then feel free to PM me for details.

Because your clocks are lower to start with you will probably not lose as much hashrate as I did with a 0.1V undervolt.  Also, because your clocks are lower, your cards will be drawing less power anyway so you might manage around 1.0125V on all three cards at under 450W.  Just as with overvolting, undervolting will give you diminishing returns; as you drop the voltage in 0.0125V increments you'll find that you'll lose larger and larger chunks of hashing power and save smaller and smaller chunks of power.  To maximise MH/J you'd probably have to go lower than 0.9875V but to maximise profit you'd be better off with something near stock voltage.  If you can handle the heat then I'd recommend going with the highest voltage that your PSU can handle comfortably and efficiently (try to find a graph of the power efficiency of your PSU).  Depending on the efficiency of your base system I'm guessing 1V or 1.0125V.

Good point. I was assuming my hash rate wouldn't take that much of a hit. I'll undervolt my current cards and see where I end up. Am I correct in inferring that you had over 400 Mh/s from your 5850 extremes at stock voltage? If so, you had some great cards to start with, and I'm not quite so lucky. My limit is about 350/375 for the two cards I have.

Yes, it's good to remind people every so often on this thread that maximising Mh/J is not the same as maximising profit.  I've seen many people complain about this on the few threads which talk about maximising Mh for fixed hardware (or hardware+clock rate).

This is a very efficient setup.  Might I enquire as to what your voltages and clock rates are for this silent mode?  Noise is the most important factor for me.

Don't forget that going larger may pay more than optimizing Mj.

I am setting up a mining data center now and the rent is paid fully and over by the savings per KWH from private rate to industrial power. That in including on site admins Requires some Investment, though.

What shotgun said.

If you are setting up a serious mining rig you will want/need more power than can be supplied via standard wall outlets and it doesn't cost any more money to have 240V outlets installed instead of 120V outlet. If you don't KNOW how to do this already, hire an electrician. Mucking about in your breaker panel without knowing what you are doing could kill you.

Less than 450W is easy, but it depends on how much hashing rate you are willing to sacrifice. I have "silent mode" for a miner with 2x5850 and 1x5870 which uses 385W, but the hashing rate is only ~920 Mh/s. I only use it on really hot days or when I don't want fan noise, though.

You're welcome.  450W for 3 cards looks perfectly possible.  Just be aware that your maximum stable clocks will reduce quite a lot. (I lost 130 MHz from both cores with a 0.1V undervolt).

Um, you shouldn't be switching the PSU to a different voltage if your electric lines aren't actually running that voltage. Ie: if your breaker is 110/120v you can't just put the PSU on 208/240v to save energy. Further more, if your breaker is 240v and you put the PSU on 120v you'll fry the PSU immediately. Finally, most PSUs these days are "auto switching" which means it will adjust to whatever voltage you plug in - so there's no switching it manually anyway.

teukon,

Thanks very much for this information. My cards are currently at stock voltage, so I will first try lowering the voltage and see where this gets me. I'm hopeful that I can add a third 5850 and not be pulling much more than I am now (say keeping it under 450w or so).

If you want to keep your temps down without maxing out the gpu fans, you could try a case fan placed above the cards or at either end, experiment with pushing vs pulling air over the cards to see what gets you the best temps.  I have a bunch of case fans pushing air down onto some of my 4 gpu rigs and that's dropping them all by about 10 degress C.  In another room I have a desk fan blowing across a couple of caseless rigs.  That's achieving a similar 10 degree drop.   I don't know exactly how much juice it uses, about 15w IIRC.

I finally took the time to give the BIOS a good stripping.  I took out everything non-essential (USB, SATA, onboard graphics, firewire, sound, and various motherboard bits) and lowered the voltages and clocks of everything I could as far as they would go (a 0.3V undervolt for CPU, RAM, and NB).  I didn't touch the special DRAM pages as they really looked quite hard.  My CPU is now at 6% usage but I don't notice any sluggishness as one might expect.  The total power saving of this was 4W so I'm now down to 300W.

Unfortunately, my card at 850 MHz crashed this morning (it lasted for 36 hours or so) so I've had to pull the clock rate back to 845 MHz and this has cost me 2.1 MH/s.

My system is mining at 722.8 MH/s (+/- 0.2) and draws 300W (+/- 3W depending on temperature) giving me 2.41 MH/J.  I've decided that the HDD stays so this is probably as far as I'm going to go with this.

In summary it seems that the most important factors for determining MH/J are:

1) Low voltages on the cards.
2) Efficient PSU (just increasing mine just from 89% to 92% would save me 10W).

Thank you all, I've sent my tips to those whose comments have helped me.

I did save changes and reboot to read the new power drain but didn't go as far as booting the system in full and running the mining software (would have taken hours to test all of the different settings).  I did notice that the power savings were negligible so I didn't bother but I have to admit the 4W in my 304W read-out bugs me.

I'm not up on AMD or Intel stuff.  I've not touched PCIe buses, northbridge, southbridge, et cetera.  Do you think that more than a 1-2W saving could be made here?

you need to reboot for BIOS changes to take effect. shut off legacy usb (if your not using it) coms, printer, sound, raid, all that. probably save only a couple watts if that though.

tried underclocking the PCIe bus? how about undervolting other chips (southbridge?). this last depends on your bios/chipset. Im not up on AMD stuff, so I may not have the right term.

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.

Reduce ram clock to about 1/3 your core clock, the 300mhz is a reference everyone throws out. I've done this on all my cards, it doesn't effect the performance. Even if you have to run it a bit higher, say 400mhz, that should be more than plenty and it's saving you 5-700mh/s of memory clock that isn't getting used.

The 6xxx series work better with 256 work size.

Haven't read through the entire posting yet, but have you tried underclocking/volting your hypertransport? Slowing down the pci/e lanes? I mean... if your card is using 16 lanes, and you only "need" one lane, then couldn't you reduce the lane to 1/16 the original speed and still maintain overall bandwidth?

Use services.msc in windows to disable stuff your pc does not need to be running. Could shave cpu cycles allowing you to slow your cpu down even further.

Edit: I get the idea you are not running windows. So scratch that last line.