(HP71B) ASM question

[J-F Garnier]

(08-05-2024 04:21 AM)brouhaha Wrote:  

(07-30-2024 07:54 AM)J-F Garnier Wrote:  I didn't know the connection to the Fairchild PPS 25.

See my comment in the HP 9199A thread, and Steve Simkin's reply.

Thanks for linking to this thread !
As Kim, I missed it at the time, maybe I misread "9199" as a TI 99xx thing (a completely different story too).

Quote:

Quote:Do you know where the Capricorn CPU architecture, used in the Series 80 and the 75C, comes from?

The HP Journal article KeithB mentioned explains their rationale for designing a custom architecture, namely BCD arithmetic and variable length data. It is unclear that any specific architecture(s) influenced it, other than the generalized influence of the BCD and variable length word of the calculator processors.
The earlier Fairchild F8 architecture (also used by Mostek 3870) was AFAIK the earliest microprocessor architecture to have 64 registers, but it doesn't really appear that it had a significant influence.

I can also think of the CDP 1802 with its 16 16-bit register bank (so only 32 bytes total).
As for the Capricorn, one of the register was acting as the program counter, but the subroutine mechanism was completely different and unusual.
Actually I used it for a project beginning of the '80s at about the same time I was discovering the HP-85 assembly language.
The 1802 was introduced in 1976, so I doubt it could have been a source of inspiration to HP.
The story of the 1802 is interesting too.

J-F