(UPDATED: Bitcoin / poclbm) Compute4Cash: Use your GPU to Make Money with OpenCL


*** Second Update (2011.02.17) ***

I just received two messages that detail what is Bitcoin and what is really Compute4Cash tool.

Here is the first message:

the Bitcoin community ( bitcoin.org ) noticed Compute4Cash today and we
found out that it is used to generate Bitcoins.

Bitcoin is a cryptographic peer-to-peer currency and it is secured by
computing power. Those who contribute computing power are rewarded with
50 Bitcoins after completing a block (“workunit”; I think Compute4Cash
splits them into smaller workunits). This is completely legit and there
are exchanges where one can sell 1 Bitcoin for roughly $1.05 nowadays.

Compute4Cash.exe is based on poclbm (https://github.com/m0mchil/poclbm),
a program used to calculate Bitcoin blocks. I even identified the small
OpenCL kernel image in the article as being from poclbm as I worked on
that code not too long ago.

An ATI 5970 will generate about 700 Bitcoins/month (this changes every
two weeks), that’s about $735. Compute4Cash claims a 5970 will net $255
so he is making about $400..500 profit.

So maybe you should encourage your readers to generate Bitcoins directly 😉

and here is the second message:

compute4cash is actually using your gpu power to make bitcoins (http://bitcoin.org), and then exchanging them for about twice as much cash as he pays you. Bitcoin is an online currency which you can exchange for cash, services, and other goods. The exchange rate is currently at about 1 USD per bitcoin. If you chose to do this on your own, rather than through the compute4cash middleman, you will make more than double the money.

compute4cash is being dishonest in telling you that this is used for computation or “data compression for the financial sector”

compute4cash is using an open-source miner called Poclbm (https://en.bitcoin.it/wiki/OpenCL_miner). At current difficulty and bitcoin price levels, the guy is making >50% profit on this. Any of you who are participating in the compute4cash pool, would do better on your own, using a free open source gpu miner. where better == about twice as much return.

I encourage you all to learn about bitcoin and cut out the middleman.
here are some links you should visit if you are interested in making money with bitcoin http://www.bitcoin.org http://en.wikipedia.org/wiki/Bitcoin http://news.slashdot.org/story/11/02/10/189246/Online-Only-Currency-BitCoin-Reaches-Dollar-Parity

*** First Update (2011.02.17) ***

Compute4Cash client is actually a wrapper around a Bitcoin miner called poclbm (Python and OpenCL).

What is Bitcoin?

Bitcoin is a peer-to-peer digital currency. Peer-to-peer (P2P) means that there is no central authority to issue new money or keep track of transactions. Instead, these tasks are managed collectively by the nodes of the network.

Then Bitcoin is a new kind of money!

More information about Bitcoin HERE.

*** Update (2011.02.13) ***
I got some information directly from Compute4Cash (at least there are some real guys behind 😉 )

The tool is used for distributed computing for the financial sector.

The program will continuously compute hashes until it finds a small enough hash to meet our requirements. Basically it is encrypted compression. The more clients we get working on this the more data we can encrypt/compress.

Compute4Cash does not wish share more information but they assure that you will not get any trouble with the law by using this tool.

From time to time, I look at Google ADs on Geeks3D.com, and few minutes ago I stumbled on this ad: “Own a Radeon 5XXX / 6XXX?” Use your video card to make money!”.

Humm… Compute4Cash is a website that proposes to pay you for your OpenCL GPU power processing. It pays you via PayPal:

Use your computer to generate some extra cash!
So you want to put your computer to work for you to make some extra cash, eh? Great! We can help you do just that. Compute4Cash will pay you for your video card’s free cycles which we will use to perform massive computations. All you have to do is register, download the Compute4Cash client, make sure your video card drivers are up to date, and run the program. The more work your hardware does for us the more we will pay you – it is as simple as that!

How we measure the work you complete
We measure the work your hardware completes in ‘Work Units’ – a Work Unit (WU) is a fixed quantity of calculations that allows us to fairly compensate users based on how much work their hardware completes.

How you get paid
Compute4Cash will give you $0.10 $0.20 USD for each WU you complete. We will deposit these funds into any PayPal or Liberty Reserve account you specify. For a quick reference, a top of the line Radeon 5970 will do around 2 WU/hr, give or take 0.50 WU depending on its core clock speed. This equates to about $150 $300 a month per card if you compute 24×7! All you have to do is run our program in the background.

Here is the OpenCL client


Update: Compute4Cash requested me to remove the code.
Just for fun I edited the exe (280KB) and an important part of OpenCL kernel is readable:

Compute4Cash OpenCL kernel

Honestly this client is a bit suspicious. Compute4Cash doesn’t tell us what exactly the client does. Maybe the client is used to do illegal stuff like password cracking (see this post for an example of MD5 cracking with OpenCL).

Sure, it would be cool to monetize the idle cycles of our GPUs but for something legal. As long as Compute4Cash remains enigmatic about the real job of the client or unless a trustworthy source has tested and approved it, I don’t recommend you to install it. According to the latest update, this tool is a Bitcoin wrapper and Bitcoin community encourage us to use a free open source gpu miner. See more details at the top of this article.

68 thoughts on “(UPDATED: Bitcoin / poclbm) Compute4Cash: Use your GPU to Make Money with OpenCL”

  1. Promilus

    It uses OpenCL 1.0 and doesn’t use CPU device.
    It is focused on pure arithmetic performance with nice usage of VLIW architecture of AMD GPUs.
    I guess it is exactly what you suspect it is – password cracking software.

  2. Compute4Cash

    You are close – our program does indeed compute hashes much the way password cracking software would do, but we do not use this code to crack passwords. This code is used to find the smallest hash of a given set of data and to do this we muse append a nonce to the data, hash it, check the size of the hash, and repeat until we find a hash small enough to meet our requirements. Effectively our program is compressing data. We certainly are not brute forcing passwords.

    FYI, you left out the bit of code that proves this – the last few lines of code call a function that compares the size of the hash to a target size and discards the result if it is too big.

  3. Stefano

    And you have to add the cost of power consumption of the graphic card.
    I think it doesn’t worth the money.

  4. Stefano

    And, from term and conditions:
    “Compute4Cash will not pay more than $600 to any one user or deposit account in any 365 day period. Doing so would incur a substantial tax related administrative overhead. “

  5. spiked_mistborn

    Seems like it could be a cool idea, but there is NO information about what kind of computations they are doing besides what you found in the exe file. A whois search on the domain says it was registered through domainsbyproxy.com, which means that there is no way to tell who actually owns this website or where they are from. Seems shady to me.

  6. Promilus

    Don’t know about USA energy prices but in Poland it’s ~0.15$ for 1kWh. You can generate more money through compute4cash client than have to pay for energy. That doesn’t change it is disturbing software – FAQ tells only there ARE WUs, and not what is made with them. It surely doesn’t look like molecular dynamics or weather simulation, more like some cryptography or intense math solution (a lot of bitwise ops).

  7. Compute4Cash

    Here’s a thought to chew on: the heat generated by your video cards when running the Compute4Cash client can be used to heat your house, so some if not all of the electricity expense involved with running the Compute4Cash client is offset by a reduction in your heating costs (in cold climates at least).

  8. Promilus

    It is a little weird system of posting comments. I believe at the time I wrote my comment right above there was none from ‘Compute4Cash’

  9. JeGX Post Author

    @Promilus: sorry, but since all comments are under moderation, I have to manually approve them, and I don’t know why, I missed compute4cash comments…

  10. JeGX Post Author

    Maybe I should stop comments on the blog and create a thread per post in the forum for discussion… What do you think?

  11. Avlin

    When you are running Folding@home, how know that it is not a nuclear bomb simulation for example ? (I’ve folding since 3 year)

    a 80+Gold PSU and a HD5850 oc let you gain more money that what you paid for current

    that is why my pc can do folding + compute4cash with free current + a litte money :p

  12. IL

    @Compute4Cash Why not use Amazon high perfomance computing instances for your project?
    You’ve mentioned HD5970/5870 as the best cards for computing. But nowadays we have HD6870@900MHz (could be oc to 1000MHz), HD6950@800MHz (oc to 840MHz) and HD6970@880MHz. Particularly I’m choosing from HD6870 and HD6950. What card would be faster for computing? What is preferable: engine clock or number of steam processors? By the way it would be nice to see stats for different types of video cards on your website.

  13. Avlin

    it scales well on gpu clock 😉

    and amazon doesn’t offer GPU

    my hd5850 @ 950 runs at 1.04 wu/hr

  14. Promilus

    “how know that it is not a nuclear bomb simulation for example”
    Because it uses molecular dynamics engine (gromacs, amber etc. cores) which is unusable for fission and fusion simulations.

  15. Compute4Cash

    We are now collecting statistics for how well various cards perform at various clock rates, at some point we will add a table with this data on our website.

    A 5970 is much better than a 6870 due to the 5970 having much more stream processors. Performance seems to be something like some_CoEff * stream_processors * core_clock. Also a 5970 can be clocked to 900Mhz+ yielding somewhere around 2.25 WU/hr.

  16. IL

    Thanks for all the answers. They shed some light on possible performance. Of course 2×5970 would be most powerful choice but the price. I think of one 6950 now and combine it with another one 6950/6970 when the price settle down. But that SmallLuxGPU graph on anandtech shows GTX 460 is similar to HD 6950 in this test. Do results correspond to computer4cash workload in the same way?

  17. fellix

    “more like some cryptography or intense math solution (a lot of bitwise ops).”

    Bingo! That’s why they prefer ATi/AMD GPUs. Radeons are much faster in integer/bitwise op’s than any current NV solution. And if the kernels are fat with little branching and high memory locality, the HD5000 and HD6000 series are perfect match for the job.

  18. JeGX Post Author

    I’m testing the tool with two HD 6970 (default clock): 1.97 WU/hr… but the power consumption of my testbed is around 500W…

  19. Avlin

    2.14 WU/hr sorry

    and the cpu is downclocked to 800Mhz

    but my room is so hoot i need to open the window !

  20. fellix

    Two GTX460s scored 0,18 WU/h for a quick test. Shamefully slow and pointless for real work, but I think this is an architectural limitation in GF104 (and GF114). Only 1/3 of all the SP cores in those GPUs are paired with a 32-bit INT ALU.

  21. Compute4Cash

    We have not tested too extensively, but we have enough data to conclude that the 5970 is the best option right now. It provides one of, if not the best WU/hr/$ rates, and it certainly provides the best WU/hr/kWh. We have not measured actual power consumption but it is supposed to be close to 300W at stock speeds and so you’ll get >2 WU/hr for <300W. We are looking forward to the release of th 6990 – we hope it will provide even better figures 😀

  22. Promilus

    @Squall – worse example you couldn’t find – that’s totally different algorithm and you can’t expect cards to fit into the same performance list in raytracer and hashing tool.
    @Wlp – HD4670 without OpenCL HW LDS has some 0.1Wu/hr at stock clocks (750MHz/2000MHz)
    That’s why I said it uses intensively AMD architecture.

  23. fellix

    I think the older HD5800 Series are better suited for this type of calculations. Their peak performance with integers is a bit higher than the new 6900 generation, me thinks.

  24. Squall Leonhart

    “@Squall – worse example you couldn’t find – that’s totally different algorithm and you can’t expect cards to fit into the same performance list in raytracer and hashing tool.
    @Wlp – HD4670 without OpenCL HW LDS has some 0.1Wu/hr at stock clocks (750MHz/2000MHz)
    That’s why I said it uses intensively AMD architecture”

    It makes use of heavy branching and seemingly double precision, which 1. 6800 series cards don’t have double precision and 2. nvidia’s opencl 1.0 profile is poorly optimised.

    AMD’s architecture isn’t superior in this case, just the opencl implementation is better.

  25. r0galik

    Hey, anybody knows how to enable GPU OpenCL support on Mobility Radeon HD 5650? I’ve got all the newest drivers and software (OpenCL SDK etc.). But still every program displays information that I only have support for CPU OpenCL. I know that graphics for laptops are generally different than for desktops, but what would be the purpose of not including this function in 5xxx series?

  26. Promilus

    “AMD’s architecture isn’t superior in this case, just the opencl implementation is better.”
    Of course it is… and C4C doesn’t use DP since it runs on HD4670 too, right? Same applies to SLG 1.7
    btw branching isn’t exactly best thing to do with OpenCL 1.0 beta for HD4k yet my results with mid card from that family isn’t that bad in comparison with GF ones with far superior OCL handling.

  27. Cuong

    @whoever know the following issue

    I use two HD 5870, driver Catalyst 11.2
    CPU i7 860, HT off. No Overlocking.
    Asus P7P55D mobo (2 pci express x16: run at x16/x4)

    If I disable crossfireX, the Compute4Cash only found 1 OpenCL GPU. The programs use exactly one OpenCL GPU from one card (1.05WU/h). No CPU power is used.


    If I enable crossfireX, the Compute4Cash found 2 OpenCL GPUs. The program uses exactly two OpenCL GPUs from two cards (2.09 WU/h) And also 50% CPU is used consistently!!!!!!

    I found out that whenever crossfirex is used, 50% CPU will be used either.

    Do you have the same problem?!

  28. Avlin


    yes exactly the same

    and i have tell compute4cash the problem and they are now working on it 😉

    it is due to wait cycle that do the cpu for waiting each GPU

    Compute@4cash say me that a next release will solve the problem

    did the x4 link perform well for the computing ? because in game x4 link is not good at all

  29. Cuong


    Thank you very much for the fast reply.

    Yes, the x4 link performs very well for the computing.

    1 card = 1.04
    2 cards = 2.06

    I can say that x4 is not a problem for computing.

    I wonder if we can only active 1 core CPU to save power. I find nowhere talks about the power consumption of one core (no HT) on i7.

  30. Avlin

    you must reduce speed to the lowest possible an voltage too, but there is no interest to disable core because unused core on i7 are automatically shutdown.

    and set the affinity to only 1 core for compute4cash.exe

  31. Cuong

    That is wonderful.
    I almost forgot the affinity function of windows.

    Thanks ever so much for your help, I really appreciate it.

  32. BlueMatt

    This is actually just a wrapper around a bitcoin miner called poclbm. It is available at https://github.com/m0mchil/poclbm. See bitcoin.org for more information. It appears the owner of the site takes around a 50% cut, whereas there are mining pools that take 2%.

  33. JeGX Post Author

    Thanks BlueMatt! Indeed, the OpenCL kernel in Compute4Cash client is the same than in poclbm / BitcoinMiner.cl.

  34. Compute4Cash

    There are several significant differences between Bitcoin mining pools and Compute4Cash:

    Compute4Cash pays users in USD for the work they complete, without any complicated or expensive currency exchanges.

    Compute4Cash pays a fixed rate not subject to market fluctuations or probability games.

    Compute4Cash uses less bandwidth than pooled Bitcoin efforts.

    The Compute4Cash client is slightly more efficient than poclbm.

    The profitability of Bitcoin pools is about to drop *significantly* when the difficulty factor nearly doubles in the next few days – Compute4Cash users’ income won’t change a bit. It may change next month when our promo period ends, but we are hoping that the numbers will allow us to not have to drop it all the way to $0.10/WU.

    The bottom line is that Compute4Cash is easier for users and more stable than pooled Bitcoin efforts are. It’s true, our profit margin is higher than that of the Bitcoin pool owners, but there is a good reason for it and we’re confident that most users will see the value in the service we offer.

  35. a

    Compute4Cash: there’s nothing wrong with running your pool – providing a lower-variance payout, and in the form of USD rather than bitcoin (which many people unfamiliar with bitcoin can understandably prefer), can be a valuable service.

    What /was/ wrong is being deceitful about what you are doing, and trying to profit not just from people’s preferences as far as payout structure, but also from people’s ignorance.

    Well, now the jig is up – and people can make an informed decision of whether they prefer to pay you a hefty cut, or to go it alone.

  36. BlueMatt

    Fair enough, as long as its out there, and not just hidden. Would also be nice for you to give credit to m0mchil, who wrote the client you are using, and possibly jgarzik if you use his/her server.

  37. Garrett

    Bah, BS Compute4Cash. You’re making a huge amount of profit, that’s how you can claim that the price you pay out won’t change. And the difficulty factor will not “Nearly double”, you liar, it is estimated to increase by maybe 40%, maximum. Nowhere near the doubling you claim.

    And then there’s the fact that, bitcoins are a superior currency to cash and people should get involved with them, in order to boost the bitcoin economy. In the end that’d make the bitcoins you’re generating worth far more than just cheating people like you are now.

  38. fuzzylogic

    TLDR @ bottom

    “Compute4Cash pays users in USD for the work they complete, without any complicated or expensive currency exchanges.”

    ****Currency exchanges with Bitcoin are not too difficult. Like every new technology, it takes a bit of time to learn the basics. In my opinion it’s worth the time to learn as you will be able to instantly trade the Bitcoins you make for over twice as much cash if you desire. Learning to use these sites takes a little while, just like learning to use ebay.
    https://mtgox.com and https://www.bitcoinmarket.com/ allow you to trade for cash. They have also been around much longer and are much more reputable and honest. There are also numerous sites that let you trade your Bitcoins directly for goods or services. Also, buying with bitcoins provides you anonymity. Download the client from bitcoin.org, get some free bitcoins by google searching for “the bitcoin faucet” and look at how it works.

    “Compute4Cash pays a fixed rate not subject to market fluctuations or probability games.”

    ****If Compute4Cash wasn’t making money they would shut down. They can easily afford to pay you a flat rate because that flat rate is already a tiny percentage of what they make from your computer’s work. Also, although it is getting more difficult to generate coins, the value of Bitcoins are increasing exponentially. (source http://bitcoincharts.com/charts/)

    “Compute4Cash uses less bandwidth than pooled Bitcoin efforts.”

    ****Compute4cash IS a pooled Bitcoin effort. They just do the cash trading for you and send you a smaller portion of what they make. If they’re so much better, why did they go through all the trouble to hide the fact that they’re using your computers to generate Bitcoins? Also, the bandwidth is only an issue to the pool operator, NOT to normal people who are using their GPU’s to generate Bitcoins (unless you’re on dialup or 3g or something)

    “The Compute4Cash client is slightly more efficient than poclbm.”

    ****This has not been verified. Even if it is more efficient they’re keeping the extra cash/bitcoins they make from the increased efficiency.

    “The profitability of Bitcoin pools is about to drop *significantly* when the difficulty factor nearly doubles in the next few days – Compute4Cash users’ income won’t change a bit. It may change next month when our promo period ends, but we are hoping that the numbers will allow us to not have to drop it all the way to $0.10/WU.”

    ****The profitability of bitcoin has been increasing since it started. More people interested in bitcoin means they’re worth more. Although the difficulty of making them yourself has increased, their value has increased more.

    “The bottom line is that Compute4Cash is easier for users and more stable than pooled Bitcoin efforts are. It’s true, our profit margin is higher than that of the Bitcoin pool owners, but there is a good reason for it and we’re confident that most users will see the value in the service we offer.”

    ****The only advantage to Compute4cash is ease of use. They take the step of converting the Bitcoins to cash for you (but this is something you can do yourself instantly after generating a block yourself (similar to what they refer to as a work unit)

    Bitcoin users wanted to inform people of the true nature of compute4cash because we saw they were making an effort to hide it. We felt they were taking advantage of the fact that few people know about bitcoin and using this situation to make more than their fair share. We want more people to get interested in Bitcoin because that’s what it will take for it to succeed as a currency. Compute4cash’s actions are dishonest and are devaluing the Bitcoin currency.

    TLDR; It’s not too hard to use your gpu in a public bitcoin pool and make more money. (Yes, you will definitely be able to make more cash if you wish to trade the Bitcoins for cash)
    Compute4cash is devaluing bitcoins by tricking people into generating them and paying much less than their market price.

    This has nothing to do with cracking passwords or breaking cryptography. If the cryptography used to secure bitcoins was broken, they would be worthless! If you still don’t believe it, please go to bitcoin.org and look at the publicly released source code. (Compute4cash does not release their source so you have no idea what code you’re running on your computer) Add to this the fact that they tried to start a business based on deceiving people.

    Also, check out the following sites and videos for more info on bitcoin. We always welcome new members to the community and would like to see some of you using Bitcoin!

  39. Compute4Cash

    It is clear that there are strong and differing opinions on this matter and it doesn’t make sense to continue this back and forth argument as it could go on forever. Every user is free to decide if they want to use Compute4Cash or not.

    The Bitcoin market and mining are highly volatile, and yes, right now Compute4Cash’s profit margin is higher than the alternatives, but these figures are always in flux and they will be changing significantly in short order.

    The next difficulty adjustment will indeed be about a 40% increase and the one after that will almost certainly be in that area as well due to the carry-over from the current difficulty.

    Let’s put an end to this arguing and let people decide for themselves whether they would prefer to participate in a stable system like Compute4Cash, or to get involved in another pooled Bitcoin effort, or to go at it alone, or to not participate at all. The Bitcoin community has successfully exposed the behind-the-scenes activity of Compute4Cash and now everyone is free to decide who their middleman will be without any question as to what Compute4Cash is acting as a middleman for.

  40. bitcoiner

    Every user is free to decide whether they want to use it or not, but they may not be aware of the alternatives.

    Now that this information is out, it would be nice if you’d put information about bitcoin on your page and tell your users what they’re really doing.

    It would restore trust in your program and encourage less technical people who are interested in bitcoin in using your client to generate money. I agree with you, your program is easier to run then setting up the python miner and bitcoin client separately.

    I’d also encourage you to offer people the option of receiving bitcoins instead of cash (or a mix of the two) and release the source for your exe. If you want the value of bitcoins to keep increasing it’s important people know about them and desire owning them. You may also want to consider paying a larger percentage. I think this would be a great compromise that could make your program more successful in the long run.

    I don’t know what your pool is generating but think, 50% of 1000 bitcoins is less than 20% of 5000btc.

    The community

  41. Compute4Cash

    FYI – as we predicted, with the jump in difficulty yesterday and the market correction today, Compute4Cash’s pay rate is quite favorable for our users – we actually netted a 3% *loss* over the last 24 hours. We will likely be offering a variable rate payment option with a fixed profit sharing ratio soon to maintain a lower fee while minimizing the risk of incurring a loss.

  42. Avlin

    install two hd5850 and get compute4cash on one card and poclbm on the second.

    then wait and compare !

    you’ll see that the best is to have an hd 5970 or two with ubuntu and poclbm 😉

    and a decent PSU (800W – 80+gold)

  43. Pingback: Compute4Cash: Estafa? Update | Team Hardware Venezuela

  44. Avlin


    but it seems crossfire is not required for multi gpu under linux

    now i haven’t tested, but under windows you can have max 4 GPU and 8 gpu with linux

    what matters here is a very good cooling and PSU !

    the OS used don’t change the rate of hash/s

  45. IL

    As for referral program it’s interesting to know if 2% are subtracted from their accounts to credit yours.

  46. Compute4Cash

    The $/WU rate has dropped significantly due to major changes in the marketplace and global competition. This is unfortunate but it is not something we can control.

    It was true that we did not have to drop the price to $0.10/WU on 3/1 – it was $0.122/WU at that time. Things have been changing very quickly however, hence the dramatic changes in the $/WU rate.

  47. Brandi

    A good friend and I have created a pool, and we are in the very beginning stages. After over a month of testing and developing on the Bitcoin Test network, we have made it live production, and are looking for some folks to join and help us make the pool better.

    Heres the connection info:
    Signup and create workers here: http://www.bithasher.com
    Point your miners here: bithasher.com port 8332

    Some info about the pool and its hardware:
    Proportional Payout
    Zero fees as we grow
    API data coming soon (We are working on it right now)
    Our servers (yes, thats plural ) are located in a very nice Datacenter located in Knoxville TN.
    We have 2 separate ISP’s providing very huge pipes to our servers
    HP Proliant main servers with IBM xSeries as a redundant backup

    What we can offer you:
    A good stable pool that is in a very reputable datacenter running very good physical hardware. We are not running this on some janky Dedicated, or VPS. We own the physical machines. We chose a datacenter that is within a very short driving distance for us, and we have 24×7 access to the racks if needed.
    Zero fees as we grow.
    We are also welcome to any and all suggestions you may have. We want this pool to be what everyone needs, and looks for in a pool.
    We are coming up with ideas that will be special awards for the first few users.
    We welcome any and all miners, regardless of how small or large your rigs are. CPU miners are just as welcome on our pool as the big 2 Ghash rigs.
    We have a forum in the works, that we plan to grow as our users suggest, and we are working on a hardware guide for new miners.

    Come and be a part of our pool, and grow with us. Help us make this the pool that you want.

  48. name

    what happened to compute4cash.com – why this site is offline? wth?

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