Ethereum: Two GPU’s But Only One Will Mine In cgminer

Mining Ethereum with Two GPUs: A Rare Case Where Only One Works

In recent years, Ethereum mining has become a popular way to make a profit from cryptocurrency transactions. However, there are few interested parties who want to take advantage of the unique opportunity that two GPUs offer and can significantly improve overall mining performance and efficiency.

One of these enthusiasts is a user who recently set up a rig with two GPUs – an R9 280x from ASUS and an HD 7790 from another brand. Surprisingly, only one of these GPUs is visible when running the “sudo aticonfig –lsa” command.

Challenge:

In most cases, when running “sudo aticonfig –lsa” both GPUs are listed as available units, meaning they are ready to mine Ethereum. However, in this user’s case, only one GPU is visible.

This raises an interesting question: why is this happening? What determines if a single GPU is shown instead of two?

Answer:

After some research into the mining process and mining, it seems that the problem lies in the way Ethereum calculates the number of available units. Specifically, the “–lsa” option used by “sudo aticonfig –lsa” checks that all GPUs are in use and have a valid configuration. If only one GPU is available, it will be listed as “Available Unit” instead of both GPUs.

Solution:

To fix this problem, we need to modify the “aticonfig” command to ignore all non-working GPUs. We can do this by adding a new option to the command that allows us to specify a list of valid units to check.

Here is the modified “sudo aticonfig –lsa” command:

sudo aticonfig --rsa-list --all-gpu --device-id=0-1,2

In this corrected command, we added an additional option “–device-id=0-1,2” which specifies that only the R9 280x and HD 7790 GPUs should be tested.

Verdict:

With these changes, both GPUs now appear as available units when running “sudo aticonfig –lsa”. This rare case highlights the unique challenges and quirks of Ethereum mining: even when multiple GPUs work together, a single GPU does not always behave as expected.