First Impressions From a 6-card Mining Rig using GeForce GTX 750 Ti GPUs

7 Mar
2014

six-gpu-rig-gigabyte-geforce-gtx-750-ti

Today we have built a 6-card mining rig using Gigabyte GeForce GTX 750 Ti (N75TOC-2GI) video cards that are based on the latest Nvidia Maxwell architecture promising very good performance for mining with low power usage. Our own initial tests of the GeForce GTX 750 Ti as a single card for mining have shown very promising results as well, so we’ve decided to see what we can expect from a mining rig and put together 6 cards with PCI-E x1-x1 extenders on an AsRock H81 Pro BTC motherboard with Intel Celeron G1820 CPU and 4GB of RAM running Windows 7.

six-gpu-rig-gigabyte-geforce-gtx-750-ti-hashrate

The result we’ve got from the 6-card mining rig for mining Scrypt with CUDAminer was a total of 1480 KHS as hashrate. Then after overclocking the video cards to the maximum stable result we managed to get (+135 MHz for the GPU and +610 MHz for the video memory) we’ve managed to increase the total hashrate to about 1615 KHS. We went as far as to increase the power target limit from the default 38.5W by modifying the video BIOS of the cards. With the modified video BIOS we have managed to get slightly more than 1700 KHS with a lot of extra power used by the whole system that made it not worth it the so little extra increase in the hashrate. Just to be sure that the x1-x1 PCI-E risers (not powered) might be the cause of slight performance drop we’ve replaced them with x1-x16 USB 3.0 powered extenders, though that did not change the performance we got from the cards.

The Gigabyte GeForce GTX 750 Ti video cards we used for the mining rig do have an external PCI-E power connector, however it seems that unlike AMD graphics with OpenCL, when using Nvidia-based GPUs with CUDA for mining the use of a x1 PCI-E lane to access the video card does introduce slight performance drop and if you multiply the 10-15 KHS less per card for a 6-card mining rig it is not so little. So it is important to know that if you are going to build a GTX 750 Ti-based mining rig you will be getting slightly lower hashrate if you are using PCI-E extenders as compared to what you will get with cards inserted in x16 PCI-E slot directly. Also there is some variation between cards in terms of the maximum overclock supported that results in different maximum frequencies that you can achieve, for example if one card is able to do +135/+700 MHz for the GPU/VRAM the second one could be maximum +100/+600. This means that in a 6-card mining rig you will need to either sync all of the cards and use the same lower settings for overclocking the GPUs to ensure they will run stable or to not have the settings synced and find the maximum for each of the cards.

Another interesting thing we have noticed is that while the use of T5x24 kernel for a single card with CUDAminer for best results, for a 6-card mining rig the use of T10x24 might sometimes provide slightly higher hashrate than T5x24, so you should try with both and see what works better in your individual case. Tomorrow we are going to be doing some more testing of the 6-card GTX 750 Ti mining rig that will be focused mostly on the power consumption as this is also a very important thing when talking about crypto currency mining.

Download cgminer 3.7.2 for Windows Scrypt mining on Gridseed 5-chip GC3355 ASICs

6 Mar
2014

cgminer-3-7-2-gridseed-windows

We now have a version of cgminer 3.7.2 available for mining Scrypt (LTC) only on the 5-chip Gridseed GC3355 ASIC devices with properly displayed local hashrate as well as HW error rate and the full cgminer 3.7.2 functionality (thanks to a user called dtbartle on GitHub). We have compiled a windows version of that miner that you can download and install it to finally have fully functional cgminer on your Gridseed Scrypt ASIC (source code available here). Have in mind that you need to install a WinUSB driver on top of the standard installed USB to COM driver for the miner in order for cgminer to detect and run on your ASIC in LTC only mode with low power consumption of about 8W.

zadig-gridseed-dualminer-usb-config

– Download and run the latest version of Zadig
– From the Zadig interface select Options and choose List All Devices
– From the Dropdown list of devices select CP2102 USB to UART Bridge Controller and click on Replace Driver with the WinUSB driver selected
– If you have multiple 5-chip GC3355 DualMiner USB devices connected you may need to repeat the procedure for all of them
– Download, edit and run LTC_ONLY.bat file from the modified cgminer 3.7.2 for Gridseed ASICs to start mining for LTC

It seems that there are some ASIC devices that may be using different virtual USB to COM drivers other than the CP2102 that our unit has (for example ST32 Virtual COM Port), unfortunately we don’t have any of those to test with. You can however try to make things work by replacing the other driver with WinUSB, just select the right name from the dropdown box (do not try to rename drivers, it is pointless) and Replace it with WinUSB (you may need to unplug and plug the USB cable to the miner after that). If after installing the WinUSB driver over the virtual USB to COM driver the ASIC does not work with cgminer, you just need to uninstall the driver from the Device Manager and unplug/plug the USB cable to the device for it to install the original USB to COM driver and it should be functioning again with cpuminer (note that this way you may have it running on a new COM port).

Do note that if running single Gridseed ASIC device you can have it connected to the system and use the hotplug 0 option, if you have more than a single miner you may have to set commandline option hotplug to 5 or 10 and then run cgminer and start plugging the USB cables of the miners (USB hubs with power on/off buttons work great for that).

– You can download cgminer 3.7.2 for Scrypt mining on Gridseed 5-chip GC3355 ASICs on Windows OS here…

How to Mine Both BTC and LTC on Gridseed 5-chip GC3355 ASIC

6 Mar
2014

gridseed-dualmining-on-windows-success

The 5-chip Gridseed GC3355-based ASIC devices that support Dual Mining for Bitcoin and Litecoin are not that easy to be used in the Dual Mode, because you need to have two different software miners running at the same time. There is a bit of specifics in what and how you need to do in order to mine both BTC and LTC at the same time and after a bit of tinkering we have managed to finally make things work as they should under Windows. You need to download a special modified version of cpuminer for Scrypt (LTC) mining and a modified version of cgminer for SHA-256 (BTC) mining. We have compiled the two software miners and you will find the download links below. You will also need the Zadig software in order to replace the virtual USB to COM driver with WinUSB driver for the cgminer to detect and work with the BTC mining side of the ASICs.

zadig-gridseed-dualminer-usb-config

– Download and run the latest version of Zadig
– From the Zadig interface select Options and choose List All Devices
– From the Dropdown list of devices select CP2102 USB to UART Bridge Controller and click on Replace Driver with the WinUSB driver selected
– If you have multiple 5-chip GC3355 DualMiner USB devices connected you may need to repeat the procedure for all of them
– Download, edit and run the BTC.bat file from the modified cgminer 3.8.5 for the Gridseed ASICs to start the miner working on BTC
– Download, edit and run LTC_ONLY.bat file from the modified cpuminer for Gridseed ASICs to start mining for LTC (check what your COM port is and edit it). You need to add the parameter “dual” (without the quotes and two dashes in front) to the command line in order for the Dual mode mining to start working

It seems that there are some ASIC devices that may be using different virtual USB to COM drivers other than the CP2102 that our unit has (for example ST32 Virtual COM Port), unfortunately we don’t have any of those to test with. You can however try to make things work by replacing the other driver with WinUSB, just select the right name from the dropdown box (do not try to rename drivers, it is pointless) and Replace it with WinUSB (you may need to unplug and plug the USB cable to the miner after that). If after installing the WinUSB driver over the virtual USB to COM driver the ASIC does not work with cgminer, you just need to uninstall the driver from the Device Manager and unplug/plug the USB cable to the device for it to install the original USB to COM driver and it should be functioning again with cpuminer (note that this way you may have it running on a new COM port).

This is it, you should have the miner running both SHA-256 (BTC) and Scrypt (LTC) mining withe the two software miners and the total power consumption should be about 60W. Note that you may need to lower the operating frequencies a bit for when mining the Dual BTC/LTC mode as the chips get hotter. If you want to mine only BTC you can stick only with running the modified cgminer, for LTC only you need the modified cpuminer without the dual option in the command line. The most attractive aspect of the Gridseed 5-chip GC3355 ASIC however remains their very low power consumption for Scrypt mining only mode, so think again if you really wan to run them in the Dual Mining more or for BTC only and not in LTC only mining mode instead.

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