FPGA-README document new hidden --icarus-options

FPGA-README

@@ -16,7 +16,23 @@ p2pool.
 
 Icarus
 
-There is a hidden option in cgminer when Icarus support is compiled in:
+There are two hidden options in cgminer when Icarus support is compiled in:
+
+--icarus-options <arg> Set specific FPGA board configurations - one set of values for all or comma separated
+           baud:work_division:fpga_count
+
+           baud           The Serial/USB baud rate - 115200 or 57600 only - default 115200
+           work_division  The fraction of work divided up for each FPGA chip - 1, 2, 4 or 8
+                          e.g. 2 means each FPGA does half the nonce range - default 2
+           fpga_count     The actual number of FPGA working - this would normally be the same
+                          as work_division - range is from 1 up to 'work_division'
+
+If you define fewer comma seperated values than Icarus devices, the last values will be used
+for all extra devices
+
+An example would be: --icarus-options 57600:2:1
+This would mean: use 57600 baud, the FPGA board divides the work in half however
+only 1 FPGA actually runs on the board (e.g. like an early CM1 Icarus copy bitstream)
 
 --icarus-timing <arg> Set how the Icarus timing is calculated - one setting/value for all or comma separated
            default[=N]   Use the default Icarus hash time (2.6316ns)
@@ -24,6 +40,9 @@ There is a hidden option in cgminer when Icarus support is compiled in:
            long          Re-calculate the hash time continuously
            value[=N]     Specify the hash time in nanoseconds (e.g. 2.6316) and abort time (e.g. 2.6316=80)
 
+If you define fewer comma seperated values than Icarus devices, the last values will be used
+for all extra devices
+
 Icarus timing is required for devices that do not exactly match a default Icarus Rev3 in
 processing speed
 If you have an Icarus Rev3 you should not normally need to use --icarus-timing since the
@@ -55,9 +74,9 @@ bitstream to the default one, use 'long' mode and give it at least a few hundred
 'short' mode and take note of the final hash time value (Hs) calculated
 You can also use the RPC API 'stats' command to see the current hash time (Hs) at any time
 
-The Icarus code currently only works with a dual FPGA device that supports the same commands as
+The Icarus code currently only works with an FPGA device that supports the same commands as
 Icarus Rev3 requires and also is less than ~840MH/s and greater than 2MH/s
-If a dual FPGA device does hash faster than ~840MH/s it should work correctly if you supply the
+If an FPGA device does hash faster than ~840MH/s it should work correctly if you supply the
 correct hash time nanoseconds value
 
 The timing code itself will affect the Icarus performance since it increases the delay after