Perhaps not write-only memory per se, but write-only registers are a pretty common thing if you do any hardware-level programming.
Though admittedly this isn't something I've done for a number of years, IIRC both the VGA and the original Sound Blaster had write-only registers which you would use to request some change in state, and some other registers that would reflect the actual current state of the device if/when the request was honoured.
Of course these are not write-only in the sense that nothing can read their contents, since they are provided as an interface to some coprocessor like a GPU or a sound chip. That coprocessor can of course read the incoming data. They are more like the hardware equivalent of mutator methods on top of private properties.
Though admittedly this isn't something I've done for a number of years, IIRC both the VGA and the original Sound Blaster had write-only registers which you would use to request some change in state, and some other registers that would reflect the actual current state of the device if/when the request was honoured.
Of course these are not write-only in the sense that nothing can read their contents, since they are provided as an interface to some coprocessor like a GPU or a sound chip. That coprocessor can of course read the incoming data. They are more like the hardware equivalent of mutator methods on top of private properties.