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@ -1,5 +1,5 @@ |
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If you wish to donate to the author, Con Kolivas, in LTC, please submit your |
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While BTC donations are preferred, if you wish to donate to the author, Con |
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donations to: |
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Kolivas, in LTC, please submit your donations to: |
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Lc8TWMiKM7gRUrG8VB8pPNP1Yvt1SGZnoH |
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Lc8TWMiKM7gRUrG8VB8pPNP1Yvt1SGZnoH |
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@ -7,7 +7,6 @@ Otherwise, please donate in BTC as per the main README. |
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--- |
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--- |
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Scrypt mining, AKA litecoin mining, for GPU is completely different to sha256 |
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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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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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that it was anticipated would make it suitable for mining on CPU but NOT GPU. |
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@ -18,11 +17,10 @@ workload, and requires you to have enough system ram as well as fast enough |
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GPU ram. If you have less system ram than your GPU has, it may not be possible |
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GPU ram. If you have less system ram than your GPU has, it may not be possible |
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to mine at any reasonable rate. |
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to mine at any reasonable rate. |
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There are 5 main parameters to tuning scrypt, 2 of which you MUST set, and |
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There are 5 main parameters to tuning scrypt, all of which are optional for |
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the others are optional for further fine tuning. When you start scrypt mining |
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further fine tuning. When you start scrypt mining with the --scrypt option, |
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with the --scrypt option, cgminer will fail IN RANDOM WAYS. They are all due |
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cgminer will fail IN RANDOM WAYS. They are all due to parameters being outside |
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to parameters being outside what the GPU can cope with. Not giving cgminer a |
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what the GPU can cope with. |
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hint as to your GPU type, it will hardly ever perform well. |
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NOTE that if it does not fail at startup, the presence of hardware errors (HW) |
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NOTE that if it does not fail at startup, the presence of hardware errors (HW) |
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are a sure sign that you have set the parameters too high. |
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are a sure sign that you have set the parameters too high. |
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@ -36,13 +34,31 @@ 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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export GPU_USE_SYNC_OBJECTS=1 |
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may help CPU usage a little as well. |
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may help CPU usage a little as well. |
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--intensity XX (-I 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. High intensities |
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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 HW errors skyrocketing. Note that if you do NOT specify an |
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intensity, cgminer uses dynamic mode which is designed to minimise the harm |
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to a running desktop and performance WILL be poor. The lower limit to intensity |
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with scrypt is usually 8 and cgminer will prevent it going too low. |
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SUMMARY: Setting this for reasonable hashrates is mandatory. |
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--shaders XXX |
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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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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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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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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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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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pointless trying to mine on. If this is not set, cgminer will query the |
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device for how much memory it supports and will try to set a value based on |
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that. |
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SUMMARY: This will get you started but fine tuning for optimal performance is |
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required. |
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GPU Shaders |
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GPU Shaders |
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7750 512 |
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7750 512 |
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@ -76,35 +92,24 @@ 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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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 HW errors skyrocketing. The low level detail is that intensity is |
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only guaranteed up to the power of 2 that most closely matches the thread |
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concurrency. i.e. a thread concurrency of 6144 has 8192 as the nearest power |
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of two above it, thus as 2^13=8192, that is an intensity of 13. |
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Optional parameters to tune: |
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Optional parameters to tune: |
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-g, --thread-concurrency, --lookup-gap |
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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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--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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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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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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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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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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R7xxx) are best at 4x. Setting thread concurrency overrides anything you put |
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into --shaders. |
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into --shaders and is ultimately a BETTER way to tune performance. |
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SUMMARY: Spend lots of time finding the highest value that your device likes |
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and increases hashrate. |
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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. This is really only of value if you |
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want to run low intensities as you will be unable to run more than 1. |
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SUMMARY: Don't touch this. |
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--lookup-gap |
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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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This tunes a compromise between ram usage and performance. Performance peaks |
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@ -112,6 +117,18 @@ 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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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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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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a thread-concurrency if you haven't chosen one. |
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SUMMARY: Don't touch this. |
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Related parameters: |
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--worksize XX (-w XX) |
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Has a minor effect, should be a multiple of 64 up to 256 maximum. |
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SUMMARY: Worth playing with once everything else has been tried but will |
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probably do nothing. |
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--vectors XX (-v XX) |
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Vectors are NOT used by the scrypt mining kernel. |
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SUMMARY: Does nothing. |
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Overclocking for scrypt mining: |
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Overclocking for scrypt mining: |
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@ -123,20 +140,23 @@ 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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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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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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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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you increase the engine clock speed further. |
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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 HW errors. |
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Suggested values for 7970 for example: |
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Third, the combination of motherboard, CPU and system ram ALSO makes a |
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export GPU_MAX_ALLOC_PERCENT=100 |
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difference, so values that work for a GPU on one system may not work for the |
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--thread-concurrency 8192 -g 4 --gpu-engine 1135 --gpu-memclock 1375 |
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same GPU on a different system. A decent amount of system ram is actually |
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required for scrypt mining, and 4GB is suggested. |
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Finally, the power consumption while mining at high engine clocks, very high |
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memory clocks can be far in excess of what you might imagine. |
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For example, a 7970 running with the following settings: |
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--thread-concurrency 22392 --gpu-engine 1135 --gpu-memclock 1890 |
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was using 305W! |
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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 |
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While BTC donations are preferred, if you wish to donate to the author, Con |
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donations to: |
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Kolivas, in LTC, please submit your donations to: |
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Lc8TWMiKM7gRUrG8VB8pPNP1Yvt1SGZnoH |
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Lc8TWMiKM7gRUrG8VB8pPNP1Yvt1SGZnoH |
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