Download Underclocking: Monarch Manual Clock and Voltage Setting

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Incorrect usage can cause failure.
Underclocking:
Monarch Manual Clock and Voltage Setting
Underclocking: Monarch Manual Clock and Voltage settings: Version 1.1
1. Summary
It is possible to manually configure the clock speed and voltage of a Monarch card. This modification is
recommended to be aimed at obtaining higher efficiency at a lower hashing speed, rather than lower
efficiency at a higher processing speed. By default every card shipped to a customer is pre-set to its maximum
operating processing speed during testing.
The table below indicates theoretical power efficiency at various speeds (+/- 10%) on 700 GH units:
Speed
Total W
W/GH
410 GH
212 W
0.51
500 GH
270 W
0.54
550 GH
339 W
0.62
600 GH
368 W
0.61
650 GH
432 W
0.66
700 GH
490 W
0.70
730 GH
530 W
0.73
780 GH
609 W
0.78
Attempting to obtain higher-than-default hashing speed from a card has to be done with extreme CAUTION
and AT USER’S OWN RISK, as it may cause over-heating of the card, leading to permanent damage to the
device.
There are two commands that can be issued to change either Frequency or Voltage. Although it is possible to
set the exact Voltage on the card, the same cannot be done regarding Frequency, as the chips main oscillator is
a Ring oscillator. Hence for Frequency, indexes are used, and it is known that a lower index is slower than a
higher index.
It must be noted that a unit, once leaves the factory, is already configured with a specific Voltage and
Frequency, optimizing it for the highest possible hash-rate. Not every frequency index will work with every
core voltage. Frequency indexes range from zero to fifteen, in regular and 2x mode.
The 2x mode is usually available (and operable) at core voltages above 600mV. Although one could set the 2x
mode for lower voltages, it generally reduces the overall performance, since many engines inside the chips
become decommissioned as they do not support 2x-mode at sub-600mV core voltages.
Underclocking: Monarch Manual Clock and Voltage settings: Version 1.1
When operating in 2x mode, the highest reachable frequency-index is two. Higher frequency indexes at 2x
mode will cause engines to become inaccurate and unstable and could cause damage to the chips. Therefore
it is recommended to use a maximum frequency index of 1 for the fast 2x operating mode.
Table below provides more information:
Core Voltage
600mV and Above
Below 600mV
Regular Mode
2x Mode Supported
2x Freq. Range
0 to 15 (0 to F)
Yes
0 to 2
0 to 15 (0 to F)
No
-
Figure 1.a – Operating Chart
2. Setting the Voltage
To set the voltage, a three-byte command must be issued to the device: ‘V’, ‘INDEX 0 to F’ and ‘X’.
For example, set the voltage to 540mV (Index-0), the following command must be sent: “V0X”.
The chart below demonstrates the relation between indices and core-voltage:
Index
0
1
2
3
4
5
6
7
Voltage
540mV
550mV
560mV
580mV
600mV
620mV
630mV
643mV
Index
8
9
A
B
C
D
E
F
Voltage
650mV
662mV
670mV
680mV
700mV
720mV
730mV
750mV
Figure 2.a – Voltage Index Mapping
Please note that the firmware refuses voltages above 630mV. This is to protect the device from over-heating.
Important Note: Although firmware refuses core-voltages above 630mV, a shipped unit, by default, may be
using higher-than-630mV core voltage. This is because they were optimized and carefully tested before leaving
Butterfly Labs. As a result, once you attempt to modify the core-voltage, you may not be able to bring it back
to what it was initially, unless you POWER-CYCLE the device.
Underclocking: Monarch Manual Clock and Voltage settings: Version 1.1
Once this command is executed, the unit will recalibrate the engines inside the ASICs. This may take up to
fifteen seconds, in which the unit will not respond to any commands. This step is required to verify all of the
engines with the new voltage and decommission the ones that fail to operate.
3. Setting the Frequency
To set the regular frequency, command: ‘F’,’<INDEX>’,’X’ can be used. This sets the frequency index in regular
mode (the slower mode). To operate in the fast 2x mode, ‘F’<INDEX>’D’ must be used.
For example, to set the frequency to index 3 in regular mode, ‘F3X’ must be submitted. To set the frequency
index to 1 at 2x mode, ‘F1D’ should be used. Once either command is issued, the on-board controller
recalibrates all the engines on the board to decommission the ones that can’t operate with the new frequency
setting. It is HIGHLY recommended to set the core-voltage to proper value before changing the frequency.
Since the on-board ASICs use Ring-Oscillators, frequency index cannot be accurately mapped to any number
(variance could be as high as 40%). Temperature and core voltage will affect the frequency as well.
4. Passing the instructions to the Monarch
You will require the latest custom version of BFGMiner for the Monarch available from
http://butterflylabs.com/drivers/
Bfgminer supports a mechanism that allows you to set both voltage and frequency on startup. The example
below will set the voltage to index 5 (i.e. 620mV) and Frequency to 2x Mode Index 0:
bfgminer <network & hashing related parameters…> --set bfl:_cmd1=F0D --set bfl:_cmd1=V5X
The command above will execute “bfgminer“, with usual network and pool-related parameters, and
further asks it to change Frequency to index-0 in 2x mode, and Core-Voltage to index 5 (i.e. 620mV).
5. Final Notes
Power-cycling the device will reset it to the shipped settings. Thus you would need to re-issue the command
with BFGMiner to underclock the unit. If the fan setup or speed has been changed and the unit resumes
hashing at the original settings it could cause adverse results for the unit.
It is not recommended to use manual clock or voltage setting commands to try to increase hashing speed
beyond what the unit was originally shipped at. Attempting to do so may easily overstress the device and
cause permanent damage to the unit and is not covered by the warranty.
Underclocking: Monarch Manual Clock and Voltage settings: Version 1.1