That is correct. I'm running mine at 750 MHz now. 800 seemed stable at first but after prolonged use caused crashes and apparently corrupted the rootfs. 900 MHz booted but froze almost immediately. I recommend everyone to check the output of dmesg every now and then. If there are UBIFS (or other filesystem) errors or kernel warnings, you'll have to lower your clock frequency and (in case of filesystem corruption) possibly do a full reflash. Many users seem to be very enthuasiastic about running at highest possible speed, so I'm expecting more cases of corruption and crashing soon. I can't be the only unlucky one