mirror of https://github.com/GOSTSec/sgminer
Con Kolivas
12 years ago
2 changed files with 145 additions and 0 deletions
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If you wish to donate to the author, Con Kolivas, in LTC, please submit your |
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donations to: |
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Lc8TWMiKM7gRUrG8VB8pPNP1Yvt1SGZnoH |
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Otherwise, please donate in BTC as per the main README. |
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Scrypt mining, AKA litecoin mining, for GPU is completely different to sha256 |
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used for bitcoin mining. The algorithm was originally developed in a manner |
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that it was anticipated would make it suitable for mining on CPU but NOT GPU. |
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Thanks to some innovative work by Artforz and mtrlt, this was proven to be |
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wrong. However, it has very different requirements to bitcoin mining and is a |
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lot more complicated to get working well. Note that it is a ram dependent |
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workload, and requires you to have enough system ram as well as fast enough |
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GPU ram. |
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There are 5 main parameters to tuning scrypt, 2 of which you MUST set, and |
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the others are optional for further fine tuning. When you start scrypt mining |
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with the --scrypt option, cgminer will fail IN RANDOM WAYS. They are all due |
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to parameters being outside what the GPU can cope with. Not giving cgminer a |
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hint as to your GPU type, it will hardly ever perform well. |
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Step 1 on linux: |
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export GPU_MAX_ALLOC_PERCENT=100 |
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If you do not do this, you may find it impossible to scrypt mine. You may find |
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a value of 40 is enough and increasing this further has little effect. |
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export GPU_USE_SYNC_OBJECTS=1 |
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may help CPU usage a little as well. |
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--shaders XXX |
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is a new option where you tell cgminer how many shaders your GPU has. This |
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helps cgminer try to choose some meaningful baseline parameters. Use this table |
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below to determine how many shaders your GPU has, and note that there are some |
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variants of these cards, and nvidia shaders are much much lower and virtually |
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pointless trying to mine on. |
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GPU Shaders |
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7750 512 |
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7770 640 |
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7850 1024 |
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7870 1280 |
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7950 1792 |
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7970 2048 |
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6850 960 |
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6870 1120 |
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6950 1408 |
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6970 1536 |
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6990 (6970x2) |
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6570 480 |
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6670 480 |
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6790 800 |
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6450 160 |
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5670 400 |
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5750 720 |
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5770 800 |
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5830 1120 |
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5850 1440 |
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5870 1600 |
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5970 (5870x2) |
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These are only used as a rough guide for cgminer, and it is rare that this is |
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all you will need to set. |
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--intensity XX |
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Just like in bitcoin mining, scrypt mining takes an intensity, however the |
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scale goes from 0 to 20 to mimic the "Aggression" used in mtrlt's reaper. The |
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reason this is crucial is that too high an intensity can actually be |
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disastrous with scrypt because it CAN run out of ram. Intensities over 13 |
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start writing over the same ram and it is highly dependent on the GPU, but they |
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can start actually DECREASING your hashrate, or even worse, start producing |
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garbage with rejects skyrocketing. |
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Optional parameters to tune: |
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-g, --thread-concurrency, --lookup-gap |
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-g: |
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Once you have found the optimal shaders and intensity, you can start increasing |
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the -g value till cgminer fails to start. Rarely will you be able to go over |
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about -g 4 and each increase in -g only increases hashrate slightly. |
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--thread-concurrency: |
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This tunes the optimal size of work that scrypt can do. It is internally tuned |
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by cgminer to be the highest reasonable multiple of shaders that it can |
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allocate on your GPU. Ideally it should be a multiple of your shader count. |
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vliw5 architecture (R5XXX) would be best at 5x shaders, while VLIW4 (R6xxx and |
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R7xxx) are best at 4x. Setting thread concurrency overrides anything you put |
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into --shaders. |
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--lookup-gap |
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This tunes a compromise between ram usage and performance. Performance peaks |
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at a gap of 2, but increasing the gap can save you some GPU ram, but almost |
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always at the cost of significant loss of hashrate. Setting lookup gap |
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overrides the default of 2, but cgminer will use the --shaders value to choose |
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a thread-concurrency if you haven't chosen one. |
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Overclocking for scrypt mining: |
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First of all, do not underclock your memory initially. Scrypt mining requires |
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memory speed and on most, but not all, GPUs, lowering memory speed lowers |
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mining performance. |
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Second, absolute engine clock speeds do NOT correlate with hashrate. The ratio |
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of engine clock speed to memory matters, so if you set your memory to the |
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default value, and then start overclocking as you are running it, you should |
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find a sweet spot where the hashrate peaks and then it might actually drop if |
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you increase the engine clock speed further. Unless you wish to run with a |
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dynamic intensity, do not go over 13 without testing it while it's running to |
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see that it increases hashrate AND utility WITHOUT increasing your rejects. |
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Suggested values for 7970 for example: |
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export GPU_MAX_ALLOC_PERCENT=100 |
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--shaders 2048 -g 5 --gpu-engine 1135 --gpu-memclock 1375 |
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--- |
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|
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If you wish to donate to the author, Con Kolivas, in LTC, please submit your |
||||
donations to: |
||||
|
||||
Lc8TWMiKM7gRUrG8VB8pPNP1Yvt1SGZnoH |
||||
|
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Otherwise, please donate in BTC as per the main README. |
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