How is Yacoin cpu mining only and doesnt work with gpu mining? I thought litecoin was suppose to be cpu mining only coin and everyone was told gpu's would not work on litecoin now look at litecoin.
Getting GPU mining to work with YAC has proved to be more difficult than most expected and while it's not impossible that there are those out there doing it, there's no proof of it and no one has come forward showing it can be done.
Here's a couple quotes of WindMaster (who's currently working on the
hard fork (client fork) for YAC and future development
https://bitcointalk.org/index.php?topic=206577.40) on GPU mining YAC and about his attempt to get GPU mining to work during the early days of release.
This one I'm unsure about. I thought for sure that if there were a significant number of GPU implementations floating around, someone was going to post one by now (as a claim to fame) as soon as GPU mining would have become unprofitable (which by my calculations is probably getting close to becoming unprofitable as YAC prices drop).
Anyone that has followed my posts through the days after the coin launched knows that I experimented with GPU implementation of scrypt+chacha20/8(N,1,1), the hashing algorithm used by YAC. I never got as far as making it work with cgminer or mining with it. I just created a basic OpenCL kernel (no cgminer interface), performed some benchmarks at various values of N, didn't bother doing any major optimizations, and decided I needed something that would go significantly faster (my GPU farm only consists of 24 Radeon 5850's and 24 Radeon 6950's), as it took me about 1.5 days to do it and difficulty was already skyrocketing. At that point I dropped it and went straight to writing a Verilog implementation for FPGA's, knowing that I could probably only pull that off up through N=32 and would have a limited time to make it happen (in the end, I got about 1.5 days of FPGA mining in before N=64).
We won't know for sure until someone posts a modified cgminer what their hash rates ended up. I stopped mining altogether at N=64, as that basically killed viability of my FPGA implementation. I can still place'n'route an FPGA design at N=64 but the projected clock rates from the Xilinx tools are dramatically slower than for N=32 with nearly 4x the logic area (meaning only 1/4 as many parallel computation cores are possible in the available logic area) and it just doesn't look like it would be worth the effort. N=128 won't even place'n'route, the design is just too dense. So at this point I'm going to state that I believe N=64 kills profitability of any FPGA attempt (with current FPGA technology) and N=128 isn't even routable and placeable on current FPGA technology (at least without going to off-chip memory, DDR3 or otherwise).
Currently I get far more YAC by buying it up on BTER than I would by mining, with any of the technologies I have available. My GPU farm is mining LTC right now. If there are indeed GPU farms mining YAC, I'd be expecting them to start switching back to LTC or BTC for profitability reasons either now or in the near future (well, unless YAC value goes way way up).
So, that's about all the answers I have at the moment.
Looking at the graphed data, it appears that N very roughly approximates Moore's law (with some step lengths being shorter than 18/24 months, and others being larger).
Assuming my data is correct, what is everyone's opinion of N's growth? Does it seem realistic to a) keep GPUs out and b) keep CPU mining feasible?
Offhand, for question (b), it appears from your data that CPU mining continues being feasible for quite a long time. Your data shows 512MB needed to calculate a hash in the year 2023, and that's an amount of RAM that I think everyone probably has available today for hashing. Disclaimer - I haven't double-checked that your data is correct.
On question (a), I doubt 512MB needed to hash is enough to exclude GPU's, especially a decade out. It may be enough to keep GPU's from having a huge massive advantage over CPU's once both technologies start having to hit slow external RAM and not fast internal L1/L2 caches, but we won't know for sure until we see what the future holds for GPU development, amounts of RAM on GPU's (and thus how many simultaneous hashes can be calculated in parallel), whether GPU's start getting massive quantities of fast L1/L2 cache like CPU's, what the ratio of L1/L2 cache in CPU's vs. GPU's looks like in a decade, etc.. Probably too early to tell. We also need to see some of the GPU implementations or adaptations of cgminer released so we can see what they're achieving for hash rates. Unlike Litecoin, where (almost) everyone derived their OpenCL implementation from Reaper, for YACoin, I suspect there were multiple independent adaptations of cgminer that occurred with no direct contact between the people performing each implementation. Too early to tell on that as well, or determine exactly how widespread GPU mining of YACoin actually was/is.
The possibility also exists that other technologies other than CPU and GPU options come into existence and widespread application during that timeframe that we can't yet anticipate, or that someone could identify a TMTO shortcut in scrypt+chacha20/8, as happened with the TMTO shortcut for scrypt+salsa20/8 that made GPU's practical for calculating Litecoin hashes.