Pushing the Gridseed 5-chip ASICs to the Maximum with a Voltmod

7 Apr


The last time we talked about voltmodding the 5-chip Gridseed ASIC devices we did what we considered the optimal voltmod for optimal performance/power consumption. Back then we discussed what could be the theoretical maximum you might be able to push the voltmod to in order to try to get the best possible overclock, though that would be achieved with an unreasonably high power usage. Well, we have decided to try out and push things to the maximum, namely replacing the R52 resistor with a 68 kOhm 402 1% SMD resistor. With this modification we were aiming to get 1400 MHz while still fitting in the power consumption that the ASIC could handle in Dual Mining mode or about 60W, however running in Scrypt only mode. With these settings we were planning to get stable around 600 KHS if we would succeed in actually running the GC3355 chips at a bit over 2 volts.


So we’ve replaced the R52 with a 68 kOhm resistor, assembled everything up (do not try to run the ASIC disassembled with this mod as you can burn the voltage regulators in a matter of a few seconds). Firing up the ASIC has shown a total power usage of about 58-61W, so pretty much what we have planned initially, however the problem was that the Gridseed device did not want to function properly at that voltage after the modification. It simply did not send any shares back to the server, neither it was showing any HW errors, through apparently the device was working and communicating with the miner software. so we do not recommend to push things so much trying to get the maximum performance regardless of the power usage, better stay at at the reasonable recommendation by using a 47 kOHm resistor which should get you close to 500 KHS at about 20W, running the miners stable at about 1150-1163 MHz. Even if we were able to get the device working properly with the 68 kOhm resistor mod and with 60W power usage it wouldn’t be reasonable to get just about 100 KHS more with an extra 40W of power. You could of course try resistors with values in between 47 and 68 kOhm to see where the maximum would be, but for us it is not reasonable to get just a few more extra KHS with double or triple the power used. Still feel free to experiment and report your finding and as usual be very careful not to burn your hardware while experimenting with it. If you go with more than 47 kOhm resistor be extra careful if running the device with the bottom of the cooler not attached as you can easily burn the voltage regulators of the ASIC!

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10 Responses to Pushing the Gridseed 5-chip ASICs to the Maximum with a Voltmod


April 9th, 2014 at 05:06

I haven’t kept up with the latest volt mod info. Is the latest and best option adding only a 47 kOHm resistor? Nothing else needed? And that could get you 500 KHS poolside? That would beat dual mining by net, after power costs, 15 cents per day per gridseed with my power rates. (used today’s LTC / USD / difficulty on coinwarz). Interesting. Would it really be 500 KHS average over 24 hours? 400 KHS, for example, would only equal dual mode. My guess is that dual mode profitably will decline so it is nice that there is this option to consider.


April 9th, 2014 at 08:40

Would it be possible for the admins to test the basic voltage mod (one of the first where you bridge 2 locations and run it at 950MHz for 404KHash/s) in passive mode and use that awesome heat tool to measure the heat? I’m slightly afraid to burn my device if I do the mod and keep it in passive mode. It being silent is my main priority at the moment.



April 9th, 2014 at 15:41

Miner, 490-500 KHS local hashrate with a 47 kOhm resistor mode, the poolside result depends on many other factors such as number of stale shares, HW errors (if any), mining for a fixed coin or auto profit switching etc…

Justsome, we have actually tested that as well with the mod for about 400 KHS, no problem in running passive if the ambient temperature is up to about 25 degrees C, the ASIC does not exceed 45 Celsius after 24 hours of running. You should however be careful with the summer coming and the raise of the ambient temperatures. Adding a slow rpm and silent fan per multiple devices can also be a good option, and it works just fine with the voltmod to get about 500 KHS.


April 9th, 2014 at 16:54

admin, thanks for the feedback and the warnings. Time to get modding! :)


April 11th, 2014 at 01:09

Hi, newb question. Trying to understand the electrical aspect of replacing the resistor. 1) Is it to increase the amount of Volts to the unit. 2) Add resistance to the amount current going true as a result of the gridseed now pulling more volts. 3) if not 1 or 2 can you please provide a little more info in terms that I maybe able to understand.


April 11th, 2014 at 12:53

MinerGuy, it is not as easy as you might think. The basic concept is the use of resistors as voltage dividers, this one is used in the Gridseeds for the PLL voltage adjustment for example, in one of the earlier voltmod publications we have covered that. You can read an easier to understand article about voltage dividers here: https://learn.sparkfun.com/tutorials/voltage-dividers/all

On the other hand the R52 replacement is a bit more complex as in terms of how it affects the voltage as it is a resistor on the input of a UPI Semiconductor UP1509 Single-Phase Synchronous-Rectified Buck Controller with 2-Bit VID Input control. Solutions like that are usually used in video cards for example in order to provide the user with the ability to control the voltage of the GPU or of the video memory.


April 13th, 2014 at 21:59

i done this mod and i can only get up to 900 mh any thing past that don’t show shares or HW alot. i trying it with cg miner.


April 13th, 2014 at 22:12

bob, which mod did you do exactly, replacing the resistor with 47 kOhm one or?


April 23rd, 2014 at 03:41

i’m used 43kohm 1% resistors resulted in 1,57V@1075Mhz
but sometimes, after few days of mining, asics go extremely hot, and power cable (from 1000w comp psu) very hot too


February 7th, 2015 at 06:14

Can you lately drawl on the resistor with a pencil to increase the voltage, or would that be a bit too much.

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