hi i have 6 card inno3d p104-100
mining zcash
simplemining
power 2000 w
motherboard: - colourful
But there is a problem which is a low speed device ... with a start. The operating speed reaches 3200 sol but after an hour or less suddenly the speed drops to 250 sol and I do not know why?


Hi mate, your core OC is too high, and 530 sol/s, seem like you run it at 100% power limit, It's a bit too much. For me, I always set power limit at 80% only.
You could test it at stock setting first. Then step-by-step OC with higher core. I mined with P104-100 as well, so far so good, for your interest, please check my tests in following thread. By the way, I think P104-100 could do better on mining ETH rather than mining ZEC.
https://bitcointalk.org/index.php?topic=2677496