> PA-RISC Performance and History

Itanium is not PA-RISC. The article is thin.

Bitsavers has an interesting paper on PA-RISC 2.0 (the jump to 64 bits). It's got a high-level introduction, and then all the actual details.

https://bitsavers.org/pdf/hp/pa-risc/PA_RISC_2.0_Architectur... (2MB file)