Any VGA monitor is inherently multisync, which does not imply that it is capable of detecting that horizontal scan is too fast to be safe. The mechanism by whi

Any VGA monitor is inherently multisync, which does not imply that it is capable of detecting that horizontal scan is too fast to be safe. The mechanism by which damage occurs involve the fact that essentially everything inside the monitor is synchronized with horizontal scan, including HV power supply for the CRT (usually even the main SMPS is synchronized with horizontal scan to reduce switching noise). And efficiency of both horizontal scan circuitry and the HV power supply depends on the incoming frequency and it is perfectly possible that some frequency (usually, but not necessarily higher than indended) will cause over voltage somewhere. I have destroyed one small monochrome VGA monitor (the kind used in late 90's on cash registers) by just blindly switching the output to some SVGA mode, it even involved quite loud bang from inside of it.