I've finally bitten the bullet and killed off GPU mining from the code and it will not be in the release I'm about to post. I have given ample warning that this was coming for some time on this forum thread and IRC about this and its time has come. It's also worth noting that even GPU mining has been used lately for botnets so cgminer once again is being flagged inappropriately as malware or a virus by various "authorities". I have left a 3.7 branch on git that is based on the last code that support GPU, OpenCL and scrypt code for those who wish to use it, but it is basically unchanged in terms of its mining code for GPUs compared with 3.7.2 which will be the last official release with GPU support. You are most welcome to fork, maintain, extend etc. the existing code provided you abide by the GPLv3 copyright restrictions that cgminer is released under. I am making a conscious decision and taking a stance to
only support bitcoin by doing this and will consider all discussions regarding alternative cryptocurrencies as offtopic from here on. It is absolutely clear that we are in a stage where only ASICs matter in mining bitcoin, and cgminer is moving with the rapidly changing landscape that is bitcoin mining.
On the other hand, I think it's time to remind people of a warning I put up on this very forum thread almost 1 year to date, as I seriously worry about the massive amounts of money people are pouring into bitcoin mining hardware without being completely informed of the fact that they're unlikely to ever recoup the costs of the hardware they're purchasing.
Yes I am most aware of the apparently hypocritical nature of only supporting ASIC mining for bitcoin and then saying it's a waste of money to do so. I believe this situation is transient for the next few months though and we need to ride it out as best we can for the future of bitcoin.
However, ASICs are a totally different ball game. They basically will redefine what mining means with bitcoin, where there is no point mining with anything else if any profit is to be made. They will make GPUs, and even FPGAs, look totally useless to mine with. 1 year from now, absolutely no one will be mining BTC on anything but ASICs, except for newbies to bitcoin mining, who will ask the obvious questions about GPU mining, and still even CPU mining.
I will sorely miss the "anyone can use their spare hardware to mine with" aspect to bitcoin mining. I honestly believe that is more true to the ideal of bitcoin, where everyone running a node was contributing to its security. However, what spare hardware people had has changed dramatically recently anyway as PCs are dramatically on the decline and people move to more portable devices with less CPU/GPU power in the form of tablets and phones etc. Alas the algorithm lends itself really well to ASIC based mining, meaning everything else will be a complete waste of time. Now while cgminer will continue to work on alternate cryptocurrencies, I honestly think all the alternative cryptocurrencies will go nowhere. The only reason to mine them is to find something that can be profitable by converting it to BTC.
Down the track, cgminer will indeed be used mostly to mine with dedicated ASIC hardware to mine BTC. GPU mining for BTC will be as irrelevant then as CPU mining is today. I don't like the fact that the network will be secured with devices from 4 or 5 manufacturers making hardware that serves only one purpose - btc mining. While BTC mining previously was still only in the hands of intel, amd and nvidia, the fact is it was not on their radar at all. Bitcoin mining was a lucky aside they did, where AMD/ATI GPUs happened to do better than anyone else, and anyone with spare cycles on their hardware could choose to contribute and earn a little on the side.
Long term, cgminer will be the lowest overhead c software to drive ASICs to do bitcoin mining, with lots of code in it that is no longer relevant to BTC mining. What I really worry about, is that new hardware will continue to come out frequently enough that people end up on a cycle of investing in hardware that basically never pays itself off as slightly newer hardware and higher diffs keep coming out. Sure at some stage the limits of technology will be reached, but given the best tech at the moment is going to be 65nm ASICs when CPUs are 28nm devices, I can see the cycle going on for some time, and then even if btc mining ASICs end up in line with CPU manufacturers, they still continue to evolve over time. Dramatic profits from ASICs will likely only last a couple of weeks at most for a lucky few. The rest of you who paid for devices that don't even exist yet will not be making any magical profit no matter how big the hashrate appears. Your proportion of the total bitcoin hashrate will remain pitiful.
Sigh...