No, the author does not source the info. I have the book in front of me and he simply says, "Dallas Semiconductor was the first to come up with the idea of changing the 8051's microcoded processor core with a hard wired one. This change has resulted in instructions taking 4, 8, 12, or 16 clock cycles per instruction..."

One thing that led me to believe the Atmel 89C52 might be hardwired is that the datasheet says "compatible with MCS-51 products" and I thought that since the MCS-51 is hardwired than maybe the 89C52 is. But I guess there's no correlation.

Thanks,
Paul