[robert_tweed]

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.