11 years, 1 month ago.

Flash accelerator setting in system_17xx.c

I've been doing some benchmarking comparing an mbed LPC1768 board to a 're-purposed' LPC1769 board. I used the mbed compiler for the mbed board and the Keil MDK evaluation version (v.4.6) for the LPC1769 board.

As I understand it, the mbed is clocked at 100 MHz and I had the LPC1769 configured to run at 120 MHz.

My benchmark code comprises mainly a number of single and double precision floating-point operations.

For some reason the results from the LPC1769 were always significantly slower than those from the mbed board.

I've just found the reason why by looking on the mbed SDK on the github page. The flash accelerator configuration is set to 4 (i.e. for CPU clocks up to 80 MHz) in system_17xx.c whereas I had mine set to 5 which is what it is supposed to be according to the NXP User Manual (UM10360). Having just found Emilio's reply in this thread about a year ago which states that it should be 5, I'm wondering whether it is considered long-term safe to run an LPC176x at full-speed with the flash accelerator configuration at 4?

Unless there are some other compiler optimization settings that I'm not aware of, I suspect my mbed LPC1768 has been running with the flash accelerator configuration set at 4 since new.