I have a problem when run USBMem Keil Example for LPC2888. I got "device descriptor read/all, error -71". And sometimes with 10 trials, the device will run for 1 or two times, but fail most of the time. I know from NXP that with old version of LPC2888 can't run at high speed, so I just bought new version of LPC2888 and try for high speed again. My LPC2888 part number is lpc2888fet180 /01, and I want to know can it run at high speed?
In this case, it wasn't a decrease but an increase in optimization levels that was needed? That is a lot better than the reverse, since a higher optimization level may be required to make critical sections fast enough.
Had it been the reverse, i.e. it fails at higher optimization levels, then I would not have liked the code and/or compiler.
A thing to think about. If optimization 0->1 is required, you may not have much safety margin so own changes to the code may push it to failure even at optimization level 1.