"The era of exponentially rising clock speeds" was already over in 2003, when the 130-nm Pentium 4 reached 3.2GHz.

All the later CMOS fabrication processes, starting with the 90-nm process (in 2004), have provided only very small improvements in the clock frequency, so that now, 23 years later after 2003, the desktop CPUs have not reached a double clock frequency yet.

In the history of computers, the decade with the highest rate of clock frequency increase has been 1993 to 2003, during which the clock frequency has increased from 67 MHz in 1993 in the first Pentium, up to 3.2 GHz in the last Northwood Pentium 4. So the clock frequency had increased almost 50 times during that decade.

For comparison, in the previous decade, 1983 to 1993, the clock frequency in mass-produced CPUs had increased only around 5 times, i.e. at a rate about 10 times slower than in the next decade.