Grin has announced plans to introduce a hard fork in July this year. This is one of four planned hard forks that will occur in the first two years of its launch. These hard forks are intended to modify their "C29" algorithm, which is intended to be "ASIC resistant" and only requires 5.5 GB of VRAM. The other algorithm that Grin supports, "C31", requires 11 GB of VRAM and is intended to be "ASIC friendly". I am not aware of any ASICs currently available to mine the cuckoo cycle coins like Grin, but there are people working on them like Obelisk. The reason for this, the first of the four planned hard forks in Grin, is to slightly change the C29 algorithm so that ASICs would not continue to work had they been built. The next two hard forks will make a similar minor tweak that makes this algorithm not work for any hypothetical ASICs and the final hard fork, 18 months from now will disable C29 in favor of the C31+ algorithms which are ASIC friendly.
All of these hard forks will cost many hours in development time, not only of the Grin developers, but also exchanges, mining pools, and anyone running a grin full node. Yes, anyone using grin will either have to update their software on these dates, which are schedule to occur approximately every 6 months or they will lose control of their funds until they do so. The Grin developers are spending countless hours creating a testnet to make sure this hard fork will go smoothly. While, I'm sure it will go well, to us this seems like a huge misallocation of resources, which led us to our decision to disable the C29 algorithm on mainnet launch of MWC. Only C31+ mining will be available for MWC on Mainnet launch.
By disabling C29 from the start, MWC will be able to avoid these planned hard forks which are very disruptive to the network. In addition, the benefits of maintaining this "ASIC resistant" algorithm are not very significant. GPUs will still be able to mine MWC, even with C29 disabled, but they will need to have at least 11 GB of VRAM. Since a GPU is available for just over $300 that meets these requirements, we don't see this is a major problem and anyone who owns a GPU that supports C29, will not even be able to mine grin in 18 months anyways based on the current roadmap so they will need to upgrade eventually no matter what. Supporting these low end GPUs just doesn't make sense and we feel was a mistake for Grin to support them in the first place. Hence our decision to drop support from day one.
To people who own C29 GPUs that were hoping to mine MWC, you will need to upgrade to a C31 GPU like the SAPPHIRE NITRO Radeon RX 570 if you want to mine MWC.