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Zoomhash, a USA-based company selling Gridseed ASIC miners has started selling voltage modified Gridseed G-Blade miners though they call them Zoom-Blade. The Blade Miners are available in two versions, a 6.2 MHS (VMOD1) that apparently can run at up to 925 MHz and 170W power usage and a 7.5 MHs (VMOD2) model that can work up to 1050 MHz with 300W power usage. There is no information about actual improvement in the power scheme of the voltmodded devices, only about improved cooling, so in our opinion if you are not very careful in what environment they are going to be placed you might have some trouble with these miners. Overheating and burning up voltage modified G-Blade miners is not that hard to get if you place them in a hotter environment and the cooling is not sufficient enough to handle the extra load.
Out experience doing a voltage mod of the G-Blade has shown that the miners are able to handle some extra voltage and be overclocked a bit with good extra cooling. Pushing them to 1050 MHz however could be more of a problem as the power block of these devices is definitely not designed to handle 150W per PCB, and even with some extra cooling you could still have problems with high temperature and that could easily lead to problems with the hardware. So we advice extra caution should you decide to go for a voltage modified G-Blade miner, or to modify your own miner. Zoomhash has apparently done tests, but if you place the miner at a place with higher ambient temperature you could still have issues with the proper cooling of the device. So be extra careful and monitor the voltage modified miners very closely at least the first 24 hours in order to be sure that they are staying cool and will be able to operate problem free for long time.
On the thermal image above you can see how things look on one of the PCBs of the new Gridseed G-Blade Scrypt ASIC in terms of temperature, the GC3355 chips of the device run pretty cool at about 40-50 degrees Celsius. These are the thermal images of the voltmodded Gridseed G-Blade ASIC that we have posted about. Do note that the thermal images are of the modified device with the additional cooling heat sinks attached to it, so the temperature of the voltage regulators is lower and the overall PCB temperature as well. You can use these if you plan on doing a voltage modification to your miners in order to see what are the possibly weaker spots – the components that get hot, in order to improve their cooling and to make sure that you will not overheat and burn your ASIC miner. We do recommend extreme caution when voltmodding the G-Blades as they are already pushed pretty close to their maximum by Gridseed and you do not have a lot of headroom for further gaining some extra performance. The power part of the Blade Miners is clearly not designed to handle much increase in the voltage, even though the GC3355 chips are just asking for more as we’ve seen with the smaller 5-chip ASIC devices from Gridseed.
Take a look at how hot the PCB gets (around 50 degrees Celsius) near the power connector and that is with about 85W of power consumption per PCB, a clear sign that the connector used is not the perfect choice for powering the G-Blades and while with the stock setup it might be Ok, you should be careful when you voltmod. Do note that we already have a large motherboard chipset heat sink attached to that side of the PCB and it does lower the overall temperature as well. It is placed on the back side of the PCB where the voltage regulators are and it helps to reduce their temperature, because the airflow from the cooling fan does pass through it as well and helps to keep it quite cool.
Looking at the side of the PCB where the voltage regulators are placed, thanks to the heat sink we have placed directly on the three VRMs their temperature is quite Ok, but there are other components that might have some issues with heat. These are the choke on the left of the voltage regulators on the photo and the 16V capacitor below the regulators as they both get to about 70 degrees Celsius in terms of temperature. And while they still do seem to work fine in the long run this may cause some issues, so you might consider replacing the capacitor with a more serious one.
Again we are going to advise you to be very careful should you consider doing a voltage modification to the new Gridseed G-Blade miners as it can be dangerous and you can easily damage your expensive miner. The modification here is not as easy as just replacing one resistor as you need to do cooling improvements as well and you are not able to push things too much to be on the safe side, so the hashrate increase is also not that big as compared to what you are getting without the modification. So you might really want to reconsider if it is worth doing the modification at all, we are probably not going to be modding another G-Blade for a while until we see how the voltage mod will handle on the longer run in its current state.
In the previous post with our first hands on experience with the new G-Blade miners we have mentioned a bit the topic about voltmodding the new Blade Miners. Now is the time to talk a bit more about it and share our experience based on the voltmod experiments we have already done on our G-Blade. We already said that the new G-Blade uses the same UPI Semiconductor UP1509 chip for controlling the voltage of the GC3355 chips as is used on the smaller 5-chip ASICs. So it is easy to do the voltage modification to the G-Blade as you are going to be essentially replacing the same resistor, though there is a bit of a difference in how things look on the new PCB. There are no element markings, so make sure you replace the right resistor marked on the photo above with a green circle with the 333 written on it. The resistor we are replacing is also a 33 kOhm one (~1.2V default), though here it is 603 type and not 402 like on the 5-chip ASIC devices, so it is easier to replace.
Do not be in a hurry to solder a new one before reading our advice. Since the default voltage of the GC3355 chips is 1.2V as on the smaller 5-chip ASIC miners here you can pretty much expect the same out of the box performance, though our tests have shown about 800 MHz to be the safest option in terms of how high you can go with no or very minimal HW errors, so a bit lower results than what we are seeing on the 5-chip ASICs. Also since the voltage regulators used on the new G-Blade are not that much powerful than the ones used in the 5-chip models you are not going to have the same safe headroom to increase the operating voltage of the chips, in fact you are actually pretty limited.
We were quite disappointed in how Gridseed has designed the cooling of the new G-Blade miners, and especially the use of a powerful and noisy fan to compensate for the lack of adequate cooling for the three VRMs. The CG3355 chips can easily be cooled with a silent and much lower RPM fan, however it seems that the powerful fan is there just to be able to ensure that the mosfets are kept cooler without having any radiators directly placed on them or on the back of the PCB where they are located. We are getting about 60 degrees temperatures of the IR mosfets at the standard voltage and operating frequency of 800 MHz, however as soon as we remove the fan the temperature of the VRMs starts to get higher very quickly while the CG3355 chips still remain pretty cool. By replacing the resistor marked above with a higher value one and increasing the operating voltage of the chips you can easily overload the voltage regulators and burn them in a matter of just a second without the fan and even with the fan running you can still burn them if they get too hot. So the moment you decide to voltmod the new Gridseed G-Blade you need to also think of improving the cooling of the voltage regulators a lot and not try to push the operating voltage of the chips too much, or you risk the VRMs easily overheating and burning up. We have used an old motherboard chipset radiator glued on the back of the PCB (with thermal glue) where the voltage regulators are placed, so that it can help in keeping them cool and have also placed a smaller video memory cooler directly on top of the regulators on the other side of the PCB.
We have slowly started increasing the operating voltage of the chips from the standard value of about 1.2V until we have reached 1.4V with the use of a 39 kOhm resistor and decided to stop there as we’ve already seen the voltage regulators getting quite hot. At this point we were aiming at a stable operating frequency of about 1000 MHz while keeping the device cooler and being on the safe side for the voltage regulators. With the 39 kOhm resistor replacing the standard 33 kOhm one we already saw the mosfets easily getting up to 90-100 degrees Celsius in about a minute (without the extra cooling). With our extra 2 radiators attached to the PCB and the chips we were able to bring the temperature below 70-75 degrees on the long run, so pretty much safe for leaving the miners run all the time like that, though you should continue to carefully monitor the temperatures. We have decided to stay at 39 kOhm, though pushing a bit more for like 40-41-42 kOhm with extra cooling might work, going for 47 or 49 kOhm may be a bit too much for the VRMs to handle. So be extra careful should you decide to go higher tan what we have used, though we do not recommend it, and monitor carefully the temperature of the voltage regulators as they may get very hot in no time and burn up without adequate cooling!
Here is what we are getting after replacing the resistor from the standard value of 33 kOhm to a 39 kOhm one. Running the device (only one of the PCBs is connected on the photo) at 1000 MHz seemed quite Ok with little HW errors, though we have decided to go a step lower in order to lower the HW errors a bit more. After some additional testing we have settled for 988 MHz as it brings down the HW errors up to something about 1-2 per hour which is much more acceptable than getting an error about every minute or so at 1000 MHz. The local hashrate at 988 MHz we are getting per PCB is close to 3.4 MHS or almost 6.8 MHS total for the whole miner with the 2 PCBs modified, up from about 2.6-2.8 MHS per board or about 5.2-5.6 MHS without the mod and the miner running at 800 MHz. The power usage per PCB after the voltage modification is about 85W or a total power consumption of about 170W for the whole modified miner.
The results we are getting are not bad, but do require you not only to solder a resistor, but also to improve cooling of the device. You also need to be extra careful should you decide do go even higher than what we have achieved as the voltage regulators might not be able to handle well the additional load or the temperature. It seems that with the G-Blades things were already pushed close to their limits by Gridseed, so there is not that much of headroom left for users to squeeze some extra performance for free by voltmodding the units. We are a bit disappointed by that, we kind of expected more, especially after seeing what the GC3355 chips were capable of in the smaller 5-chip devices. We are going to be doing some more tests and experiments in the next few days to see if we can get something better than what we are already getting, but the chances for some significant improvement are not that good.
Again we advise anyone willing to do a voltage modification to his Gridseed G-Blade ASIC miner to be extra careful as these devices are more expensive and can handle less abuse from the users as compared to the smaller 5-chip ASIC miners, so proceed with caution! The smaller 5-chip miners allowed more headroom as they were designed to handle much higher power usage because of the BTC mining part, but for the new G-Blade miners Gridseed has decided not to support the SHA-256 mining part (the chips do, but the device cannot supply enough power, so do not try to activate BTC mining or your miner may burn). So the headroom for overclocking without doing some modification related to the voltage regulators is actually very little with the new G-Blade ASIC devices, and working only on improving their cooling does help only a bit. Reworking the power part of the miner could open up some additional possibilities, but that is not something that most users can easily do themselves unlike the replacement of a single resistor for example. In short, if you are expecting performance boost on the bigger G-Blades like on the smaller 5-chip devices with a voltmod, you will be very disappointed, and the fact that after voltmodding the Blade Miner you might have trouble cooling it down properly for long term operation might not be worth the extra performance boost you will get.