A search in the cuda documentation will. But to save you the trouble, it means compile for the compute 1.3 architecture. Quoting directly from the output of nvcc:
--gpu-architecture <gpu architecture name> (-arch)
Specify the name of the class of nVidia GPU architectures for which the cuda
input files must be compiled.
With the exception as described for the shorthand below, the architecture
specified with this option must be a virtual architecture (such as compute_10),
and it will be the assumed architecture during the nvopencc compilation stage.
This option will cause no code to be generated (that is the role of nvcc
option '--gpu-code', see below); rather, its purpose is to steer the nvopencc
stage, influencing the architecture of the generated ptx intermediate.
For convenience in case of simple nvcc compilations the following shorthand
is supported: if no value for option '--gpu-code' is specified, then the
value of this option defaults to the value of '--gpu-architecture'. In this
situation, as only exception to the description above, the value specified
for '--gpu-architecture' may be a 'real' architecture (such as a sm_13),
in which case nvcc uses the closest virtual architecture as effective architecture
value. For example, 'nvcc -arch=sm_13' is equivalent to 'nvcc -arch=compute_13
Allowed values for this option: 'compute_10','compute_11','compute_12','compute_13',
Because I want to ensure both of them passed to gcc when it compiles host code, and that it the way to achieve it. It ensures both are treated as an argument to the Xcompiler nvcc argument.