Abstract: A computer. When an instruction calling for an architecturally-visible side-effect in an architecturally-visible storage location is recognized, a value is stored representative of an architecturally-visible representation of the side-effect, a format of the representative value being different than an architecturally-visible representation of the side-effect. Execution is resumed without generating the architecturally-visible side-effect. Later, the architecturally-visible representation corresponding to the representative value is written into the architecturally-visible storage location. On a context switch, a context of a first process is written and a context of a second process is loaded to place the second process into execution. At least some instructions maintain results in storage resources outside the context resource set, and instructions are marked to indicate whether or not a context switch may be performed at a boundary of the marked instruction.