Quote from: xeridea on November 20, 2016, 03:35:18 AM

Quote from: nerdralph on November 20, 2016, 02:01:14 AM

Quote from: xeridea on November 19, 2016, 09:59:17 PM

Quote from: nerdralph on November 19, 2016, 04:34:56 PM

I'm getting 150 sol/s on my Rx 470, and even your 155 is still below the 160 sols/s limit I calculated. If the 164 Sols/s you are seeing on the Rx 480 is with a 1750Mhz memory clock, then that is ~95% of my 173 sols/s instead of 93%. It's possible the refresh may only impact the burst transfers and not the command rate, which could mean no impact on the 173 sols/s since less than 75% of the burst transfer slots are being used.

If someone writes a miner that gets substantially more than 173 sols/s (i.e. ~200 sols/s) on a Rx 470 with 7Gbps memory, that would be conclusive proof that there is a way to avoid the limit as I calculated it. I've discussed my ideas with other miner developers, and I have considered various ways of reducing the external GDDR bandwidth requirements. I doubt anyone will find a serious mistake now. Something I just noticed is that the L2 cache on Polaris/Ellesmere is 2MB (512KB/controller), compared to 128KB/controller on previous chips like Tonga. That is still too small, IMO, to be of much (more than a few %) help.

Computer scientists and mathematicians have studied sorting problems for decades, and I am convinced that sorting n random records requires at least n reads plus n writes. With some work it should be possible to implement an equihash algorithm where the average amount of data manipulated per round is 16 bytes per record. A GPU with a 32MB cache would then be limited to it's cache bandwidth instead of the external GDDR5 bandwidth.

Yeah I was basing on 480 4GB, since 470 seems somewhat compute limited on CM 7.0. Since it is around the theoretical max, I am thinking there may be ways to get a bit more, some tricks to save some bandwidth, but of course we can't know since we are not CM. He says he figures 300H is possible on 390X, which currently gets 230, but it will take a lot more work.

https://bitcointalk.org/index.php?topic=1670733.msg16924145#msg16924145

300 for a 390x is 1.73x the 173 limit I calculated for a Rx 470. The 384GB/s memory bandwidth of the 390x is 1.71x the 224GB/s memory bandwidth of the Rx 470. I'd say that's not a coincidence, and Claymore has come to the same conclusions that I have about the limits of ZEC mining performance.

Hmm, I was thinking 390x had 320GB/s memory bandwidth, I guess that's the 290x. It seemed right since 390x isn't much faster than 480 at Ethereum. Its bout 27% faster Ethereum, and 27% faster Ethash (as of CM 7.0, and many revisions before, this is general trend). Both algorithms are affected by timings, though less so with newer CM versions. Your estimate seems reasonable, I am just speculating. I don't do side projects programming these days, developing hand issues, so I can just speculate Sad

CM 8.0 getting 187Sol/s on 480 4GB (7Gbps), and 176 on 470 4GB (7Gbps), Stock clocks, so it seems 173 is not the theoretical limit.