On October 16, the Ethereum network will experience a planned hard fork, as the Byzantium update will be released, bringing increased mining rewards but also setting a hard End Of Life (EOL) limit for all mining GPUs with 3GB of RAM.
Byzantium aims to prepare Ethereum for a future switch to Proof of Stake (PoS). The Proof of Stake is a much different algorithm to validate transactions and achieve distributed consensus than the current Proof of Work (PoW) Ethash algorithm which depends on energy-intense computations conducted by GPUs to solve a mathematical problem – a process called ‘mining’ as it is rewarded with new Eth coins.
Among other features, the Byzantium hard-fork will bring increased block mining speed (estimated ~14.1 sec) which means lower transaction times for Ethereum users. For Ethereum miners who use their expensive GPUs for Eth mining 24/7, this means increased revenue. So Byzantium seems to be a win-win for both.
At the same time, the higher block generation speed means that the Ethereum’s Directed Acyclic Graph (DAG) file will be increasing faster than before. In Ethereum, a DAG file is a vast randomly generated dataset used by Ethereum’s PoW algorithm, Ethash A new DAG is created every epoch (every 30000 blocks or ~100 hours ) using the Dagger-Hashimoto Algorithm.
Given that all mining GPUs need to load the DAG in their memory, a faster increasing DAG size means that graphics cards with 3GB RAM, such as a nVidia 1060 GTX, will become "obsolete" for mining sooner than it was expected before the Byzantium release.
With Byzantium in place, the DAG size is expected to reach 3GB on block 6,900,000. But because a GPU has an 80Mb overhead, all 3GB GPUs will be useless for Ethereum mining even sooner. This moment will be on block 6,750,000 when the DAG size will reach 2.92GB.
Thus, owners of 3GB GPUs need to know that their cards will stop mining Eth at some moment between November 12 and November 13, 2018. In other words, GPUs with 3GB of RAM will be mining Eth for another 13.5 months after the Byzantium update.