SDRAM runs nominally at VIO Voltage: 3.3 volts. It should have no problems at 3.5 volts (which is what ASUS motherboards are default set to), and should be fine up to about 3.8 volts. I'd be reluctant to run any higher than about 3.9 volts...that's really way too high.
As for DDR SDRAM, which runs at 2.5 volts, I'd not be willing to run higher than about 2.9 volts.