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GPU-Based Mining And Mining Programs

All About Bitcoin Mining: Road To Riches Or Fool's Gold?
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GPU-Based Mining

GPUs are based on SIMD (single instruction, multiple data) architecture, where hundreds of threads can execute the same program in parallel, operating on different input data. Thus, the difficult task of feeding billions of input data vectors into SHA-256 is now spread out over hundreds of GPU cores.

Surprisingly, Nvidia cards are all but unsuitable for Bitcoin mining because SHA-256 is an all-integer algorithm. While Nvidia cards (at least some of them) may rule the roost when it comes to floating-point performance, they lack some integer instructions that are sorely needed for SHA-256. Thus, when similarly-priced graphics cards from Nvidia and AMD are compared, the Nvidia cards are typically slower by a factor of five to seven. This makes them utterly unprofitable for Bitcoin mining. Bitcoin mining is an application segment where AMD Radeon cards shine undisputedly.

Once very popular among Bitcoin miners, but now somewhat dated, the Radeon HD 5830 card boasts 1120 stream processing units. But that doesn’t mean it literally has 1120 separate cores. Rather, the GPU employs 224 SIMD cores, each of which sports five ALUs operating in parallel (VLIW5).

Only a well-optimized GPU program can keep all five ALUs operating at 100% utilization. But the OpenCL compiler does a surprisingly good job of spreading out operations across the available ALUs, and can keep approximately 4½ ALUs fed on average. A card operating at AMD's factory settings runs at 800 MHz, but Bitcoin miners typically overclock their GPUs. As all data of the double SHA implementation fits into the GPU registers, there are only few accesses to DRAM memory. Consequently, miners actually underclock the RAM in order to reduce the card's overall power consumption, allowing more significant overclocking of the all-important Cypress GPU.

Equipped with two Cayman processors, the Radeon HD 6990 was AMD’s top-of-the-line graphics card up until recently. A gamer can also mine Bitcoins on this card when not playing through the latest shooter, or dedicate it to Bitcoin mining after upgrading to the brand-new 7990. Between the two GPUs, the Radeon HD 6990 sports a whopping 3,072 stream processors at 830 MHz. As the Radeon HD 6900-series cards replaced the VLIW5 configuration with VLIW4, a change that benefits ALU utilization, we can calculate that each GPU has 384 processors sporting four ALUs each.

Mining Programs 

Bitcoin miners have a choice among several mining programs, for instance cgminer, BFGMiner, DiabloMiner, poclbm, and Phoenix. A more recent release of any one of them may contain a slightly more optimized version of the OpenCL-based mining program, while others may do a better job of auto-overclocking graphics cards. Some of these mining programs can also control FPGA-based mining hardware, or even the latest ASIC-based equipment. Personally, I use cgminer and I’m quite happy with it. While older versions would crash every few weeks or so, this problem seems to have been fixed in recent versions.

Required input parameters of a mining program are the URL of the mining pool, including the port number, and the user name and password for your mining pool account. There are also some optional parameters, controlling fan speed and overclocking for instance.

Benchmarks: Radeon HD 5830, HD 6990

Above: Two Radeon HD 5830 cards mining. Below: One Radeon HD 6990 card mining with both GPUs.

While a single Radeon HD 6990 achieves about 700 MH/s (total) with its two GPUs, the old 5830 only mines at approximately 250 MH/s.

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Top Comments
  • 12 Hide
    phenomiix6 , June 9, 2013 11:37 PM
  • 12 Hide
    dannyboy3210 , June 9, 2013 10:39 PM
    A very interesting read. I had been reading about Bitcoins (mainly because I just couldn't figure out what they were exactly), but this clears a lot of things up.
    Also, at the bottom of page 5, in the Comparison of FPGA and ASIC Chips table it says "Power Fraw".
Other Comments
  • 8 Hide
    Darkman69 , June 9, 2013 9:49 PM
    Finally a proper write up on Mining Bitcoin with the good the bad and the reality.
  • -9 Hide
    esrever , June 9, 2013 9:54 PM
    How does mining new coins make sense if there will ever only be 21 million? I am so confused by that point.
    Another thing is, with an economic system like this, a billionaire can easily manipulate market prices and make extremely large amount of money and still be completely fine due to this being in a grey area of the law. You can't pump and dump stocks legally but it seems pretty easy for something like this considering you can dump the bit coins off as currency in any country.
  • -5 Hide
    s3anister , June 9, 2013 10:00 PM
    Quote:
    How does mining new coins make sense if there will ever only be 21 million? I am so confused by that point.


    To quote the Bitcoin wiki page: "The last block that will generate coins will be block #6,929,999 which should be generated at or near the year 2140."

    So to directly answer your question, the whole reason for mining bitcoins is because you'll most definitely be dead before the last block chain is even completed.
  • -6 Hide
    smeezekitty , June 9, 2013 10:14 PM
    Shitcoins definitely = fools gold!
    Huge waste computing power IMO
  • 1 Hide
    vmem , June 9, 2013 10:27 PM
    Quote:
    Shitcoins definitely = fools gold!
    Huge waste computing power IMO


    someone needs to rewrite the algorithm and somehow hook up block generation to folding@home or some similar constructive use of the computational power.
  • -1 Hide
    smeezekitty , June 9, 2013 10:28 PM
    Quote:
    Quote:
    Shitcoins definitely = fools gold!
    Huge waste computing power IMO


    someone needs to rewrite the algorithm and somehow hook up block generation to folding@home or some similar constructive use of the computational power.

    That would be a great idea. Verifying a relatively small hash to screen out the cheaters then perform something useful like F@H.

  • 12 Hide
    dannyboy3210 , June 9, 2013 10:39 PM
    A very interesting read. I had been reading about Bitcoins (mainly because I just couldn't figure out what they were exactly), but this clears a lot of things up.
    Also, at the bottom of page 5, in the Comparison of FPGA and ASIC Chips table it says "Power Fraw".
  • -8 Hide
    slomo4sho , June 9, 2013 11:02 PM
    Fiat currencies... I guess for some people the dollar wasn't worthless enough.
    It is amazing how you can lose your "wallet" and your funds permanently disappear from the pool.
  • -9 Hide
    toarranre , June 9, 2013 11:02 PM
    Never heard of this and I'm quite confused by it. Use graphics cards to find units of a currency that from what I can tell must be extremely succeptable to artificial inflation or all out collapse.
  • 12 Hide
    phenomiix6 , June 9, 2013 11:37 PM
  • 9 Hide
    csf60 , June 10, 2013 12:53 AM
    In 2010 I started bitmining and reached 3 bitcoins in 2 months with a 5850. Each bitcoin was worth 3$ at that point so I just gave up and lost my wallet. If I only knew 3 years later they would change for 150$ each... :face palm:
  • 3 Hide
    choz , June 10, 2013 12:58 AM
    Thanks for your calculations. I now have more things to laugh about here in Australia when I read about bitcoin "miners" setting up multi-gpu rigs when our power price is around the 25c per KWh mark and rising by 5% annually.
  • 0 Hide
    ET3D , June 10, 2013 1:16 AM
    I've only skimmed the article, but I didn't see a good discussion of mining pool, trading and all the DDoS, phishing and hacking that goes with it.
    The technical aspects and financial calculations are one thing, but going bitcoins is somewhat of a hornets' nest, and it's really worth discussing this stuff.
    I haven't mined seriously, but the first time I tried (for two weeks, generated half a bitcoin), I left the bitcoins in the pool and one of the pool's founders embezzled and took what was there and left. I've seen other pools hacked, and there are regular DDoS attacks on them, changes in the terms, all kinds of things you really need to follow carefully if you want to mine effectively. Just leaving your miner running and hoping that you'll get the expected coins eventually doesn't cut it.
    I currently mine a little LTC for fun (partly because after installing Catalyst 13.4 I can't mine BTC and can only mine LTC with an old cgminer version I have installed). I'm not sure that it's worth it financially, and I'll probably shut down mining in the not too far future.
  • 4 Hide
    Madn3ss795 , June 10, 2013 1:19 AM
    Quote:
    I bought a few Radeon HD 7790 graphics cards

    7790 already out in June 2011 ? :lol: 
  • 2 Hide
    immanuel_aj , June 10, 2013 2:28 AM
    Quote:

    Or better yet, enjoy this crazy sideshow from the bleachers.


    Yup, that's exactly what I'll be doing! There's always something in the news about it every month these days. :) 

  • 5 Hide
    uruquiora , June 10, 2013 3:05 AM
    this is why i think TH is one of the best IT news website around nowadays... thanks for a very interesting article and for sharing the good and the bad with newbies like me on that subject.
  • -1 Hide
    somebodyspecial , June 10, 2013 3:29 AM
    Maybe now we won't have to see this in benchmarks. It's over for gpus.
  • 0 Hide
    tlg , June 10, 2013 4:17 AM
    I am also wondering how he got the HD7790 in June 2011, except if this is a typo because later on in the same page he talks about November 2012.
  • 0 Hide
    dalmvern , June 10, 2013 6:05 AM
    Great article, I have been wondering what the fuss was all about. Now the only question I have is:
    What is all this processing power being used to do?
    As it was mentioned in an earlier comment, it would be great to use it for something like scientific research like F@H...but I have never seen anything explaining IF it is being used, and if it is, what it is being used to do.
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