I'm using Quartus Prime Standard 18.1 and trying to program a serial PROM device SST25VF016 in Active Serial mode. Programming cycle succeeds but is extremely slow, takes more than 3 hours for 16Mbit. Any ideas?
You're using a SPI Serial NOR Flash from Microchip for configuring a Cyclone IV FPGA via AS mode. The SPI Flash device has a HOLD# signal. Can you probe the HOLD# signal and find out if this signal is being held low for long period of time. If this HOLD# signal is kept low , it would temporarily stop/halt the serial data transfer. Where have you connected this HOLD# signal on the board/FPGA?
Also check the status of the WP# signal. This should not be low during configuration
The device can work at 25MHz as well as 80MHz. Make sure you are operating it at 25MHz. If its still slow, try reducing this clock frequency to 10MHz/6MHz and see if configuration happens faster.