GPU overclocking to increase hash/sec

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D3ad0ne
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GPU overclocking to increase hash/sec

Post by D3ad0ne » Wed Nov 04, 2009 6:38 pm

As many of you know overclocking the shader clock on the GPU can increase the effective hash cracking speed of that GPU. But can overclocking negatively impact finding a key? For example could a overclock produce errors that would cause a computed MD5 to return the wrong result?

I have been overclocking my GTX 295’s a very small .64% from 1242 to 1250, giving a mere (1.92 B/sec * 6 GPUs ) = 11.52 B/sec increase in integer operations a second. Which really only translates to about an extra 25.36M/sec in speed. But I’ve seen people overclock 10% or even as much as 18.5% to 1472Mhz for gaming. Now this is a theoretical gain of ((((240 * 1.472) – 298)) / 398) = 138M/sec * 6 GPUs = 832M/sec – 5%) = 790M/sec

I would like to go a little further to 3 -5% (128-213M/sec increase) overclock which brings me back to my original question. Could even a mild overclock negatively impact finding a key?

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Re: GPU overclocking to increase hash/sec

Post by BarsMonster » Wed Nov 04, 2009 6:42 pm

D3ad0ne wrote:As many of you know overclocking the shader clock on the GPU can increase the effective hash cracking speed of that GPU. But can overclocking negatively impact finding a key? For example could a overclock produce errors that would cause a computed MD5 to return the wrong result?

I have been overclocking my GTX 295’s a very small .64% from 1242 to 1250, giving a mere (1.92 B/sec * 6 GPUs ) = 11.52 B/sec increase in integer operations a second. Which really only translates to about an extra 25.36M/sec in speed. But I’ve seen people overclock 10% or even as much as 18.5% to 1472Mhz for gaming. Now this is a theoretical gain of ((((240 * 1.472) – 298)) / 398) = 138M/sec * 6 GPUs = 832M/sec – 5%) = 790M/sec

I would like to go a little further to 3 -5% (128-213M/sec increase) overclock which brings me back to my original question. Could even a mild overclock negatively impact finding a key?
Basically yes, you can miss a key. In the worst cases BarsWF would detect computation errors and will show you an error.
But rare errors (like 1/trillion operations) are almost undetectable :-)

You might start from running FurMark + AtiTool (at the same time) to roughly validate stability. Main problem is overheating anyway (especially when you increase voltage).

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Re: GPU overclocking to increase hash/sec

Post by D3ad0ne » Wed Nov 04, 2009 6:55 pm

So my guess is that even a stock speed card could produce errors if it where defective or running hot. Conversly a properly running overclocked and cool card could run faster without producing any errors.

It would be nice if there were a program to stress the cores with known computational output and detect if there where miss calculations. Allowing you to overclock the shader clock then test it for stability. Does FurMark or AtiTool validate stabilty or do you simply try and detect artifacts?

For me I prefer not to overvolt the cards, in addition the room has a dedicated A/C system and stays at ~ 22C constantly.

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Re: GPU overclocking to increase hash/sec

Post by BarsMonster » Wed Nov 04, 2009 7:27 pm

D3ad0ne wrote:So my guess is that even a stock speed card could produce errors if it where defective or running hot. Conversly a properly running overclocked and cool card could run faster without producing any errors.
Exactly. I was thinking about adding selftest to barswf.
For me I prefer not to overvolt the cards, in addition the room has a dedicated A/C system and stays at ~ 22C constantly.
Well, who said that manufacturer's voltage is best for you? :-)
My card have 1.26v stock, I am running 0.85v 99% of the time (with 20 times less power consumption) and 1% at 1.36v

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Re: GPU overclocking to increase hash/sec

Post by D3ad0ne » Wed Nov 04, 2009 7:33 pm

Well, who said that manufacturer's voltage is best for you?
Good point I never thought of it that way. But this is where a "selftest" option could come in handy. Would be useful for both overclocking and under volting :)

*Edit*
Was doing some reading else where and found this:
To test for max shaders, what I do is use Folding@Home GPU client. If the shader speed is beyond its maximum, it will throw up early_unit_end or guarded run errors within the program.

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Re: GPU overclocking to increase hash/sec

Post by Rolf » Wed Nov 04, 2009 9:45 pm

FurMark actually stresses GPU's nicely, dont know if it's valid for shader domain stability testing.

Any1 wants to write Linpack for GPU's ? :wink:

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Re: GPU overclocking to increase hash/sec

Post by BarsMonster » Wed Nov 04, 2009 9:56 pm

Rolf wrote:FurMark actually stresses GPU's nicely, dont know if it's valid for shader domain stability testing.
Well, I was doing extensive tests, that's not enough. FurMark gives maximum GPU temperature, but to detect errors under that load one have to use AtiTool which actually validate render results.
ATiTool alone cannot heat card well enough to cause failures.

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Re: GPU overclocking to increase hash/sec

Post by LordMike » Thu Nov 05, 2009 9:51 am

Bars, maybe make a gpu cracker, that goes through 200-500 Million hashes once overclocked.
Then once not overclocked, do the same process and check if the results are equal.

If not, errors are possible. If so, overclocking is valid.

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Re: GPU overclocking to increase hash/sec

Post by BarsMonster » Thu Nov 05, 2009 10:02 am

LordMike wrote:Bars, maybe make a gpu cracker, that goes through 200-500 Million hashes once overclocked.
Then once not overclocked, do the same process and check if the results are equal.

If not, errors are possible. If so, overclocking is valid.
Yes, that is what I was thinking of. That is worth even for non-overclocked cards :-)

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Re: GPU overclocking to increase hash/sec

Post by D3ad0ne » Thu Nov 05, 2009 2:56 pm

I would imagine something that you cound run and it would initially just use a counter from say 1-50k, the counter would create an MD5 for each count and hold it in memory. Then it would just loop through the counter again and again verifying if the the output matched what was in memory.

Code: Select all

error = false
while (ct >= 50000)
{
   MD5List(ct) = MD5(ct);
   ct++;
}
ct = 1;
do {
while (ct >= 50000)
{
   MD5Check = MD5(ct);
   if (MD5Check != MD5List(ct) {
	error = true;
	}
   ct++;
}
} while (error = false);
Perhaps even better would be to scale the list to fill all the video memory so that if you were overclocking memory it would identify errors with that as well.

Overall it would be really neat for someone to have a CUDA only benchmarking tool / stabilty tool. They could call it CUDAMark :)

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Re: GPU overclocking to increase hash/sec

Post by D3ad0ne » Thu Nov 05, 2009 4:49 pm

I made a estimated hash calculator using excel. Thought someone may find it useful.
Cuda Hash Cal.JPG
CUDA Hash Calculator.zip
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Last edited by D3ad0ne on Thu Nov 05, 2009 7:38 pm, edited 1 time in total.

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Re: GPU overclocking to increase hash/sec

Post by Rolf » Thu Nov 05, 2009 6:36 pm

I find it useful, D3ad0ne !
1 issue bothers me, though : 128 shaders of 8800 GTX equal to 9800 GTX IF both equal in clock.Is there no way to "define" generations ?Ofc, If there is no official info/loads of test, that's not possible to do.

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Re: GPU overclocking to increase hash/sec

Post by D3ad0ne » Thu Nov 05, 2009 7:49 pm

Is there no way to "define" generations ?Ofc
The way I understand it is that speed of calculations is strictly based off your (clock speed * shader count). If you had a 8800 GTX and over clocked it from 1350 to 1688(9800GTX) you theoretically would be able to do the same amount of integer calculations a second or hashes a second. The advantage of having newer core is better efficiency. Thus usually better clock speeds.

For me the estimated stock calculations where only .27M/sec off what I was seeing in BarsWF. It would be interesting to see how far it is off for other people.

If the numbers are right for the 300 series with just 4 GTX 380's you could do over 7.82 Billion hashes a second. With 4 GTX 395 you could do 14.66 B/sec :o (I came up with the 1500Mhz clock speed for the 395)

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Re: GPU overclocking to increase hash/sec

Post by Rolf » Fri Nov 06, 2009 11:53 am

D3ad0ne wrote:With 4 GTX 395 you could do 14.66 B
Wicked! :crazy:

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Re: GPU overclocking to increase hash/sec

Post by BarsMonster » Fri Nov 06, 2009 1:07 pm

How about 2.6*2*4 = 20.8B with 4x5870x2? :crazy:

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Re: GPU overclocking to increase hash/sec

Post by Rolf » Fri Nov 06, 2009 7:12 pm

That's even better, but AMD lacks support of it's computing language.It looks like they dont actually care about it.

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Re: GPU overclocking to increase hash/sec

Post by Sc00bz » Sat Nov 07, 2009 8:49 am

BarsMonster wrote:How about 2.6*2*4 = 20.8B with 4x5870x2? :crazy:
That's 8 GPUs ATI only supports 4 GPUs. Also a 5870x2 is called 5970.

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Re: GPU overclocking to increase hash/sec

Post by LordMike » Sun Nov 08, 2009 5:00 pm

Sc00bz wrote:
BarsMonster wrote:How about 2.6*2*4 = 20.8B with 4x5870x2? :crazy:
That's 8 GPUs ATI only supports 4 GPUs. Also a 5870x2 is called 5970.
lol :P

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Re: GPU overclocking to increase hash/sec

Post by Crucifix » Thu Nov 19, 2009 12:50 am

What exactly is the formula to determine hash cracking strength of graphics card? I know it involves shaders and clocks.... :wall:

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Re: GPU overclocking to increase hash/sec

Post by D3ad0ne » Thu Nov 19, 2009 2:21 am

Approximation is, shader freq * SP / 398 - ~5% = Hashes per second.

Example GTX 285: 1476 * 240 = 354240 / 398 = 890.05 - 5% = 846 Million hashes /sec

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Re: GPU overclocking to increase hash/sec

Post by Crucifix » Thu Nov 19, 2009 2:52 am

D3ad0ne wrote:Approximation is, shader freq * SP / 398 - ~5% = Hashes per second.

Example GTX 285: 1476 * 240 = 354240 / 398 = 890.05 - 5% = 846 Million hashes /sec
Thanks! Going out to get an HD 4830 in a couple days and was wondering what kind of speed to expect...800m/second sounds pretty good for a $50 card. Hoping to break 1 bil with an overclock.

Although that doesn't seem to make sense for my current card--hd 3870, 320SP@875MHz and still only at about 350m/second. But for everything else it seems accurate.

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Re: GPU overclocking to increase hash/sec

Post by D3ad0ne » Thu Nov 19, 2009 3:41 am

Ahh sorry this was for Nvidia only, for Ati it is:

This really only applies to the 4800 series:
Stream processors * clock / 398 - ~21% = Million hashes per second.
So for the 4830:
640 * 575 = 368000 / 398 = 924.623 - 21% = 730.45 M/sec
Last edited by D3ad0ne on Thu Nov 19, 2009 4:15 am, edited 2 times in total.

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Re: GPU overclocking to increase hash/sec

Post by Crucifix » Thu Nov 19, 2009 4:01 am

D3ad0ne wrote:Ahh sorry this was for Nvidia only, for Ati it is:

This really only applies to the 4800 series:
Stream processors * clock / 398 - ~21% = Million hashes per second.
So for the 4830:
640 * 575 = 368000 / 398 = 924.623 - 21% = 730.45 M/sec
Ok, thanks -- that does seem to make a lot more sense.

So, at that rate I'd need around 780 MHz core to reach 1 bil/second...that is towards upper limit of what that card can do with stock voltage.

this'll be good fun I suppose.

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Re: GPU overclocking to increase hash/sec

Post by D3ad0ne » Thu Nov 19, 2009 4:24 am

So, at that rate I'd need around 780 MHz core to reach 1 bil/second.
According to those estimations you would need a 37% overclock to 788Mhz core speed to achieve a 1 B/sec speed, minus whatever your CPU can do. A 37% increase seems kinda high, but a quick search around I see that people have got at least 700Mhz or around a 22% increase or about 891 M/Sec. Remember if you overclock to far it can cause incorrect MD5 calculations. So you will need to verify if your overclock is not producing any errors for several hours before locking it in at that speed.

I have also updated the excel sheet to support ATi, just select the Ati tab at the bottom to switch to ATi view.
CUDA-Stream Hash Calculator.zip
Nvidia CUDA & ATi Stream hash calculator
(25.34 KiB) Downloaded 489 times

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Re: GPU overclocking to increase hash/sec

Post by Crucifix » Fri Nov 20, 2009 11:36 pm

D3ad0ne wrote:
So, at that rate I'd need around 780 MHz core to reach 1 bil/second.
According to those estimations you would need a 37% overclock to 788Mhz core speed to achieve a 1 B/sec speed, minus whatever your CPU can do. A 37% increase seems kinda high, but a quick search around I see that people have got at least 700Mhz or around a 22% increase or about 891 M/Sec. Remember if you overclock to far it can cause incorrect MD5 calculations. So you will need to verify if your overclock is not producing any errors for several hours before locking it in at that speed.
Yup. I have seen people hit 775 MHz with no voltage or BIOS mods of any kind on 4830s, just depends on what model and whether you get a good or bad batch of GPUs. Like many things overclocking luck is a big factor.

I don't think the GPU itself is very limited, it is mostly just going to be heat that will present a problem.

I have also updated the excel sheet to support ATi, just select the Ati tab at the bottom to switch to ATi view.
CUDA-Stream Hash Calculator.zip
Thanks, nice program.

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