Topic: 475+ Mhash/s 5870 - Voltage mod and overclock - page 2. (Read 7100 times)

Look above.



I knew you could do it! 1.35V?

what watercooling block are you using on the card?

very nice, here is what i'm getting:

Clocks:
Temps
Ye ol' Mega Hash

I'm sure i could get better though, aint touched the voltages yet

Broke 500MH/s.

That's exactly what I did with my HIS 5870s

I'm still giddy about getting my hands on such an awesome card for that cheap!

Excellent, 490 MH/s from a single GPU is the highest I've seen on this forum by a margin.

Also, thank you rethaw for the highly informative post.

Honestly, the only reason I don't overvolt all the time is due to noise.  Profit/Loss are card longevity are practically irrelevant compared to my quality of life.

Haven't tried it yet but may consider.

My H²O setup is as follows:

CPU Block: EK Supreme HF (Gold)[/li][/list]
GPU Blocks: EK-FC5870 (Acetal/Copper) and (Plexi/Nickel)
Radiators: Black Ice SR1 480, Feser XChanger 480, and Feser XChanger 240
Pump: Laing DDC 3.2
Reservoir:  Danger Den 5.25" Dual Bay Res
Fan Controller:  Sunbeantech Rheosmart 6

GPUs average around 34-38°C.  VRMs don't get above 85°C.

Wow, nice. Have you used poclbm's failback for handling the disconnects?

Have you posted more info about what blocks/water cooling setup you have? What temps are you getting?

I will almost certainly try bumping up at least one of my cards now.

The highest I run mine are in my sig.  No issues for the past few months.  I do have occasional disconnects from pools but that isn't the cards.

Ok, you will satisfy your curiosity and find what is the maximum stable clock for mining, but is it worth it apart from that? Probably not.

A quick comparison: mine are @ 960Mhz Core = 440Mhash/s, so you get 35Mhash/s more = 0.6BTC more a month than me for the much higher chance that your card will die much sooner than mine. What about electricity?

I was wondering if you would be willing to play around with some electromigration numbers. The Mean Time to Failure (MTTF) due to electromigration has been estimated empirically using:



Where A is the cross-sectional area, J is the current density, n is a scaling factor that is usually set to 2, k is the Boltzmann constant, Ea is the activation energy of the material, and T is the temperature. (link)

Lets take a VERY conservative MTTF based on your estimation of two years. You are welcome to provide your own adjustments, but based on my experience the temperature has not changed much raising the voltage and overclock. This may just be due to favorable cooling circumstances but I will assume the temperature sensor readings are accurate.

So Ea, T, k, and A are all constant or nearly so. This leaves us with the current density being the most important change. For non-ohmic materials like semi-conductors J can be expressed as:



Where sigma is the capacitance, E is the electric field, D is the diffusion constant, q is elementary charge, and n is the electron density. Therefore in calculating the current density D, q, and n are constant for the same component. Then we can look at the electric field inside our component. For the sake of simplicity we assume that we are dealing with a small wire where E = V / d. Again d remains the same and the electric field grows linearly with voltage.

The purpose of the analysis above is to show that current density grows more or less linearly with increasing voltage in our case. This means for for n=2, MTTF will reduce by the inverse square of the change in voltage. Doubling the voltage reduces the MTTF of the junction by 4, quadrupling by 16, etc.

Therefore by increasing the voltage by .1V we reduce the MTTF by roughly 15%. For the given two years the MTTF for any given junction will reduce by 3.5 months.

(change in MTTF) ~ (modded V / stock V)^-2

Given 2 years is a fairly conservative estimate of the life of your card you may be reducing the total lifetime by a much higher amount, but the percent reduction in mean time to failure will be the same. For the sake of completeness I will estimate the difference in hashes over the life of a card in the two circumstances. I will give a very bullish reduction in life based on the calculations above of 2 weeks (even though in fact it was about 100 hours).

Overclock at stock voltages of a 5870, 425 Mhash/s for 2 years (104 weeks) ~= 27 x 10^18 hashes
Overclock at 1.25 V, 470 Mhash/s for 90 weeks ~= 26 x 10^18 hashes
Untested! 1.35 V, 490 Mhash/s for 77 weeks ~= 23 x 10^18 hashes

Therefore, you are correct you will reduce the overall hashes your card will be able to perform based on the MTTF. Also, there are numerous other points of failure and I believe electromigration in the junctions is just one to consider.

I would like to further complicate this picture by suggesting that having an extra 20 MHash/s now will be worth much more than the entire hashing power of the card at the end of two years given difficulty increases. I have not calculated this and difficulty changes are not predictable that far ahead. But you can see that increasing difficulty is an exponential and decreasing MTTF is quadratic.

I look forward to other considerations in ramping up the voltage before I do so.

Don't worry, I'm sure we're all aware of the various issues with overclocking/overvolting.  This thread is more about finding and establishing the limits of the cards for fun and to satisfy curiosity.  Furthermore, what we learn can be applied to design very efficient setups.

My occasional forays into the world of high voltage have all been experimental and my discoveries have allowed me to reach a stable 430 MH/s on stock voltage (5850).

Also I've noticed you like to make the assumption that miners are primarily interested in profit but perhaps this is not a safe assumption of the people using a thread with 'voltage mod' in the title.  I expect there are some passionate overclockers on this board that are taking great joy in the sudden interest Bitcoin is drawing to overclocking.

You guys are nuts to try running a 5850 or 5870 at nearly 500mhash/s.

Those cards cost $150 to 200 bucks at the least & 1.25-1.3 voltages will 100% surely kill the card due to electromigration or VRAM failure within a month or two.

It'd last years if you ran it at 420-430mhash and the monetary 'loss' is negligible considering you don't have to buy a new GPU

Also the power consumption will skyrocket if you go past 1.25v

I've not seen anyone claim a hash rate that high on a single GPU before but people do occasionally get higher core clocks.  Last night I took my 5850 (non-reference, Sapphire 5850 Xtreme) to 1.25 V and managed to get 461.1 MH/s out of it for 3 hours.  The card crashed immediately when I started up a second miner on another card in the same system.

• 1110 MHz core clock
• 370 MHz RAM clock
• 55*C GPU temperature

This is on Linux with Catalyst 11.6, SDK 2.1, and phoenix (latest phatk kernel).  Here's a screenshot of me about an hour into the pooled mining test.

This same card went to 1140 MHz before crashing and is perfectly stable at 1030 MHz at stock voltage so you might put this down to luck.

I only have experience with 5850s but I'm hoping they are similar enough to 5870s that some of the following can be of help.

I'm assuming you're using the very latest phatk kernel; check out http://forum.bitcoin.org/index.php?topic=25860.100 if not.

I found that SDK 2.1 is a few MH/s faster than SDK 2.4 on my card so I'm guessing you'll see a similar improvement with SDK 2.1 (yes, that's with phatk).

Have you tried increasing your RAM speed a little.  I know 300 MHz known to be good but I've found that as core clock rises, the maximal RAM speed rises.  You may well find another 3 MH/s or so by bumping up to 355-360 MHz.

Another idea I have is to use Catalyst 11.4.  On my card this gives a straight up 9 MH/s boost to my 5850 clocked at 900 MHz.  Over 1GHz I'd expect 10 MH/s or more.  Windows users have claimed 12-13 MH/s over me by using Catalyst 11.4 instead of Catalyst 11.6 (same card, clock, RAM, kernel, SDK, miner settings).  Unfortuately, no-one seems to know of a way of overclocking a card past BIOS limits using Catalyst 11.4 in Linux but it seems like you've solved this by flashing your BIOS to increase the limits.

May I ask how much variance you get with your hash rate?  You may need to look at your command line options (for phoenix '-a 1' - for poclbm '-e 1' maybe, I'm not sure).  If your MH/s is varying by more than 1 MH/s then you can surely manage further gains through configuration, especially if you are using Linux.  I'm guessing that this is not a dedicated miner given that you are using the '-f 15' option but if it is and it's running Linux then PM me for some further tips.

If all goes well you should be able to comfortably climb past 480 MH/s, maybe touch 490 MH/s.

Nice I'll do that too.

That's the same voltage that AMD GPU Clock Tool sets the GPU to any time you move it off stock clock settings.  I just got one of those $190 HIS 5870s from NewEgg and it seems pretty stable at 1050.  Anything over that it starts getting a little shaky though.  1050 is good for around 460MH/s but I scaled it back to 1030MHz for stability.

I used RBE to overvolt to 1.25V. It seems like at that voltage I can get pretty near 1100Mhz before it locks up. My question is, anyone gone higher? I am curious about what bumping up the voltage another .1 will offer given my temps are fine. I am on air cooling using poclbm -f 15.

If there is interest I can update with my rejected percentage after a few hours of running.