undervolt antminer s3

[mooseCavalry]

In respect to RayJay who provided the pictures and the instruction, i want to share this with you.

It is quite simple after you have dismanteld your S3.
Find the resistor with 2,088KOhm
http://imgur.com/sCfgOQo.jpg

Measure the resistance
https://i.imgur.com/a97YGg1.jpg
https://i.imgur.com/KGefeHj.jpg

Apply pencil to the side of the resistor until you are somewhere between 0,900 and 0,950KOhm.
With 0,900KOhm and a the Frequency set to 150Mhz my S3 is hashing at 310GH/S with 185Watt on the Wall constantly.

Happy mining  

Bottom Line Up Front: is this modification a "one-way street"?

I'm more a software guy, but I'll take a stab at this.

Postulation: The graphite from the pencil enhances the electrical conductivity of the resistor, effectively lowering its resistance. The result: voltage supplied by the S3 hashing board to the BM1382s is effectively reduced.


If the above is correct, I pose the following:

1. Can the S3/3+ chips run at their default frequency/clockrate once this modification is applied?

Experience with CPU over/under clocking+volting leads me to believe that if the voltage supplied is less than sufficient for the desired frequency, the chip will either fail to initialize or initialize and misbehave. See #2 particularly if false;


2. Can the graphite be safely removed?
(Methodology requested if true).


Thanks,
moose

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[alh]

Bottom Line Up Front: is this modification a "one-way street"?

I'm more a software guy, but I'll take a stab at this.

Postulation: The graphite from the pencil enhances the electrical conductivity of the resistor, effectively lowering its resistance. The result: voltage supplied by the S3 hashing board to the BM1382s is effectively reduced.


If the above is correct, I pose the following:

1. Can the S3/3+ chips run at their default frequency/clockrate once this modification is applied?

Experience with CPU over/under clocking+volting leads me to believe that if the voltage supplied is less than sufficient for the desired frequency, the chip will either fail to initialize or initialize and misbehave. See #2 particularly if false;


2. Can the graphite be safely removed?
(Methodology requested if true).


Thanks,
moose

The simplest answer to #2 is to use the other end of the pencil (i.e. the eraser).  You could also consider an alcohol soaked swab. The graphite isn't permanent by any means. You are just trying to clean it off, it isn't embedded nearly like it is on paper.

[mooseCavalry]

eraser

<facepalm>

Seems legit.  I'll post some results after kill-a-watt arrives in the mail.

[RichBC]

It's been suggested I post this here.

I decided to try my hand at Undervolting the S3, I would like to play with the S5 but am hoping the second hand prices will come down a bit first.. Although there are posts around that say you can change the core voltage using the Advanced setting field, like some others have found on my S3 & S3+ it seems to make no difference to the voltage.

I wanted to be able to easily adjust the voltage so I soldered in 2 x 4 channel 5K digital pots across the VFB resistors. These are setup with an Arduino, which also measures the voltage set..



In practice I have just rediscovered what other have found, but it's good to see the numbers for yourself.  

The Standard S3 with 218.75MHz clock had a core voltage of 0.8V hashed at about 440GH & took 321W at the wall giving J/GH of 0.73

After trying a lot of frequencies and voltages I decided it was possible to continue at 218.75MHz with the voltage reduced to 0.73V. This gives a small number of hardware errors .001% but improves the J/GH to 0.65. I soldered 4K7 resistors into the S3 an am letting it run, while continuing to play with the S3+ with the digital pots.

At my electricity cost this moves me from Break Even to about £1 Week profit. I am happy with this for the moment as it's buying BTC and my Wife is happy as it's drying the washing.

As would be expected as you drop the frequency and Core voltage the efficiency increases and the J/GH drops.

The best I have seen was at 125Mhz, 0.64V Core Voltage, giving a hash of about 254GH which is J/GH of 0.48. This was with 270 Ohms across the VFB resistor and at this point I run out of adjustment on the core voltage as we are very close to the TPS533355 0.6V reference voltage. However I am actually surprised that the chip was still hashing at this voltage.

I could probably squeeze a slightly better result by doing away with half the DC-DC converters and moving to 4 chips per, as the currents are now much reduced. I may try this later?

Rich

Here is a summary of where I have got to. I had to increase the core voltage slightly at 125MHz as with more testing I got an x....

Code:

MHz	V Core	GH	W	J/GH	R Ohm
206.25	0.728	412.5	271	0.66	4700
150	0.69	300	165.6	0.55	1800
125	0.64	250	122.4	0.49	330

The R Ohm is the value of the resistor soldered in parallel with the existing VFB resistor.

The watts for the 206.25Mhz were measured at the wall, the others were calculated from the Voltage & current drawn from the PSU on the bench so might be slightly out, but will be very close.

Rich

[Lumanet]

Hi everyone,

can someone please explain something to me.
If you look at the discussion above we seem to work on R17 but what about R20 ?
So I measured and found out those 2 are the 2 resistors which do run parallel. But when you replace both let's say with 1.8Kohm which should result in the same result like discussed above suddenly with the proper settings :

150 MhZ
0.65 V

it consume suddenly 900Watt of the wall. Anyone any explanation about this?

Thank you

Lumanet

[elrippo]

Hi everyone,

can someone please explain something to me.
If you look at the discussion above we seem to work on R17 but what about R20 ?
So I measured and found out those 2 are the 2 resistors which do run parallel. But when you replace both let's say with 1.8Kohm which should result in the same result like discussed above suddenly with the proper settings :

150 MhZ
0.65 V

it consume suddenly 900Watt of the wall. Anyone any explanation about this?

Thank you

Lumanet

Then you have obviously done something wrong if it consumes 4 Times the Energy than other VoltMods

Mine is running at 150MHZ with constantly 330GH/S and 170W at the wall....

[RichBC]

Hi everyone,

can someone please explain something to me.
If you look at the discussion above we seem to work on R17 but what about R20 ?
So I measured and found out those 2 are the 2 resistors which do run parallel. But when you replace both let's say with 1.8Kohm which should result in the same result like discussed above suddenly with the proper settings :

150 MhZ
0.65 V

it consume suddenly 900Watt of the wall. Anyone any explanation about this?

Thank you

Lumanet

R17 & R20 are not in parallel. R17 goes from the Buck Converter Output voltage to the VFB input. R20 goes from the VFB input to ground. R17 is the one to adjust or change.

Also remember you need to make the same change on the other 7 resistors on the other Buck Converters, then repeat for the second board.

Rich

[Lumanet]

Hi everyone,

can someone please explain something to me.
If you look at the discussion above we seem to work on R17 but what about R20 ?
So I measured and found out those 2 are the 2 resistors which do run parallel. But when you replace both let's say with 1.8Kohm which should result in the same result like discussed above suddenly with the proper settings :

150 MhZ
0.65 V

it consume suddenly 900Watt of the wall. Anyone any explanation about this?

Thank you

Lumanet

R17 & R20 are not in parallel. R17 goes from the Buck Converter Output voltage to the VFB input. R20 goes from the VFB input to ground. R17 is the one to adjust or change.

Also remember you need to make the same change on the other 7 resistors on the other Buck Converters, then repeat for the second board.

Rich

Got it guys :-)

I just swapped out the R17 resistor and it's partners against 1Kohm 1% SMD resistors and now I am hashing like it should be :

Under 200Watt and over 300 Ghs with the rest of the settings from above :-)

THX all


Lumanet

[underachieved]

Would this be considered the best resource here for under volting the S3?

[RichBC]

Would this be considered the best resource here for under volting the S3?

It is just a thread on undervolting the S3, there are others which you can search for, as to which is the best is up to decide. 


Rich