Turn on the overtemperature shutdown in the bitstream, and control the temperature in the mining software. It is easy.
Turn on overtemp shutdown in the bitstream
AFAIK theres no such magic button. If you want temp monitoring and thermal limits with an FPGA you have to include them in your design logic.
False. The better fpgas(like virtex 5/6, complete series 7 and newer xilinx) has pin terminals to an separated internal die temperature sensor transistor. A properly designed board should use it for temperature measurement and shutdown. It works even when FPGA isn't configured. An alternative is using jtag to read XADC (7 series and newer).
I actually went ahead and RTFM'd the "UltraScale Architecture SYStem MONitor User's Guide". It looks like it is very close to being a "magic button", it takes only one line of code:
set_property BITSTREAM.CONFIG.OVERTEMPSHUTDOWN ENABLE
On the other hand the whole guide to the SYSMON block has 113 pages, so it must be also relatively easy to accidentally mis-configure it.
I stand corrected, I was not aware of the existence of that flag! I knew you could read the XADC, but did not realize there was a bitstream flag. Good to know, although I dont know if I would rely on that as your only protection.
I appreciate the wealth of knowledge and skill coming out on this forum regarding the FPGA work.
Regarding workstation GPUs, I said they could be useful for mining, and can work alongside FPGAs given the direct access to their memory, not that they were better than normal GPUs for mining or that they were like FPGAs. You can however very often find large batches of the older generation passive cards for cheap as most people dont have the ability to use them. I last paid $130/ea about a month ago for a bunch of older FirePro workstation cards that are now hashing at 24MH ea.