Topic: undervolt antminer s3 (Read 26469 times)

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

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

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

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

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

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

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  

I've got a dozen (12) S3's and a similar amount of C1's.
Need to do this mod on all of them.
I have strong electronics and soldering skills.
So soldering in a 2.2K 1% 1/8W metal film resistor across the 2.088K SMD resistor isn't an issue. A time consuming PITA, but easily doable.
Understand everything (and the theory behind it) in the post except the "HW .003 20 ment. idle".
Is that a S/W configuration thingy?

WTF over? LOL.

Thanks in advance.

No!
the voltage field is obviously without any function.

Same as the S5, it also has no voltage settings.

I was able to duplicate these results on 2 units by paralleling a 2.2k across the resistor between VFB and Vout for each TPS53355 switcher (8 per board). That's all I did, I didn't upgrade my firmware or change voltage settings in firmware (not available in mine and read that the setting doesn't do anything anyway). I tested efficiency at different frequencies and the best results I achieved are:

Unit 1: 0.645 J/Gh @ 193 MHz
Unit 2: 0.625 J/Gh @ 175 MHz

At $0.13/kWh and current BTC price I'm profitable again, but just barely.

I have 3 more S3+ units to convert and did notice that one of the boards is a different (newer) version. I don't see the TPS53355 switcher on it or a voltage divider circuit that I can modify to change the hashing chips voltage. Any info on the newer board appreciated. I can post pictures of mod and detailed drawing if anyone is interested.

antminer s3+ undervolt

here is the better result

update new firmware
310gh
freq. 150
adv. config voltage 065
HW .003 20 ment. idle

how to drop voltage

parallel 2.2k resistor on VFB to Vout resistor

.68 for 2.2k
.75 for 6.8k

https://i.imgur.com/mxxI2t6.png
https://i.imgur.com/Zw3El3U.png
https://i.imgur.com/VL9AGvu.png
https://i.imgur.com/5oGshqw.png

https://bitcointalksearch.org/topic/m.10214088
https://bitcointalksearch.org/topic/m.10222598

I dont see a point in undervolting s3's or s3+'s or even spondoolies miners. Even with spondoolies which allows for control over the voltages lowering the pcie power from 12v starts increasing the power usage at the wall. The psu i used has a range from 12v all the way down to about 9.7v and the lower i went the higher the consumption was. Thats with a sp20 that is underclocked using the web interface so it wasnt maxed out or even at stock speed so u would thing it would make the watts per gh go down but it just kept goin up. I went from about 600w with 12v to over 700w on a bit more then 11v. I didnt want to push the psu ne furthereven though i could have but really the efficiency wont go ne further. The s3's r the same way too.

I did however find a way to make s5's much much more efficient at slower hashrates but the biggest thing most will notice is the fan noise is much much lower and i might even go as far as to say its quieter then the s3 double fans but maybe im used to it so ne thing lower is much much lower lol. The only other thing to do before considering the undervolting as being a guaranteed solution is to get longer cables that run from the boards to the controller so i would need 4 per controller....2 would be the norm length while the other 2 would be a few inches longer. If ne one has the part number for the cable connector please pm me with it so i can buy some and make my own if bitmain doesnt sell slightly longer ones separately but im waiting for them to reply.

antminer s3+ undervolt

here is the better result

update new firmware
310gh
freq. 150
adv. config voltage 065
HW .003 20 ment. idle

how to drop voltage

parallel 2.2k resistor on VFB to Vout resistor

.68 for 2.2k
.75 for 6.8k

https://i.imgur.com/mxxI2t6.png
https://i.imgur.com/Zw3El3U.png
https://i.imgur.com/VL9AGvu.png
https://i.imgur.com/5oGshqw.png

https://bitcointalksearch.org/topic/m.10214088
https://bitcointalksearch.org/topic/m.10222598