Merge pull request #168 from grzegorzszczecin/master

Extend low_power_mode to do up to 5 cn hashes at a time.

1 files changed, 14 insertions, 0 deletions

diff --git a/doc/tuning.md b/doc/tuning.md
index 8b28a43..53e682b 100644
--- a/doc/tuning.md
+++ b/doc/tuning.md
@@ -10,6 +10,8 @@
   * [Add more GPUs](#add-more-gpus)
   * [Increase Memory Pool](#increase-memory-pool)
   * [Scratchpad Indexing](#scratchpad-indexing)
+* [CPU Backend](#cpu-backend)
+  * [Choose Value for `low_power_mode`](#choose-value-for-low_power_mode)
 
 ## Windows
 "Run As Administrator" prompt (UAC) confirmation is needed to use large pages on Windows 7.
@@ -93,3 +95,15 @@ export GPU_SINGLE_ALLOC_PERCENT=99
 
 The layout of the hash scratchpad memory can be changed for each GPU with the option `strided_index` in `amd.txt`.
 Try to change the value from the default `true` to `false`.
+
+## CPU Backend
+
+By default the CPU backend can be tuned in the config file `cpu.txt`
+
+### Choose Value for `low_power_mode`
+
+The optimal value for `low_power_mode` depends on the cache size of your CPU, and the number of threads.
+
+The `low_power_mode` can be set to a number between `1` to `5`. When set to a value `N` greater than `1`, this mode increases the single thread performance by `N` times, but also requires at least `2*N` MB of cache per thread. It can also be set to `false` or `true`. The value `false` is equivalent to `1`, and `true` is equivalent to `2`.
+
+This setting is particularly useful for CPUs with very large cache. For example the Intel Crystal Well Processors are equipped with 128MB L4 cache, enough to run 8 threads at an optimal `low_power_mode` value of `5`.