For those who has flashed to 800mhz or 900mhz. You will have to try and stress the cpu to max speed at 100% to see if it is actually stable. Because 90% of the time, the cpu never uses 900Mhz for more than a couple of seconds at a time. If you want to try about 25 seconds of 100% at max speed, try launching HAM. HAM will use 100% of the cpu at max speed (even at 900Mhz) for the first 25 seconds or so. If this is good, then just try all the usual stuff that you do. The only other apps which may fully max out the cpu constantly are superpi calculations, SETI, game emulators, extracting big compressed files etc.