  We introduce the concept of smart radio environments, currently intensely
studied for wireless communication in metasurface-programmable meter-scaled
environments (e.g., inside rooms), on the chip scale. Wireless
networks-on-chips (WNoCs) are a candidate technology to improve inter-core
communication on chips but current proposals are plagued by a dilemma: either
the received signal is weak, or it is significantly reverberated such that the
on-off-keying modulation speed must be throttled. Here, we overcome this vexing
problem by endowing the wireless on-chip environment with in situ
programmability which allows us to shape the channel impulse response (CIR);
thereby, we can impose a pulse-like CIR shape despite strong multipath
propagation and without entailing a reduced received signal strength. First, we
design and characterize a programmable metasurface suitable for integration in
the on-chip environment ("on-chip reconfigurable intelligent surface"). Second,
we optimize its configuration to equalize selected wireless on-chip channels
"over the air". Third, by conducting a rigorous communication analysis, we
evidence the feasibility of significantly higher modulation speeds with shaped
CIRs. Our results introduce a programmability paradigm to WNoCs which boosts
their competitiveness as complementary on-chip interconnect solution.
