Which calculators run RPL under the hood?

[Jonathan Busby]

(11-29-2019 05:26 PM)Christoph Giesselink Wrote:  Even more, what about the 71B, the first calculator with the Saturn 1LF2 CPU which was later replaced by the 1LK7 CPU which was necessary for the HP18C. Major difference between 1LF2 and 1LK7 is the addional opcode

PC=(A)

necessary for RPL execution. To be complete, the other opcode new in the 1LK7 was RSI ("level 1" instruction set).

The HP28C was the last calculator with a Saturn CPU (1LK7) on a single chip. All later solutions use a chip combining a Saturn core and peripherals all equipped with the "level 2" instruction set.

Are you sure? I don't remember if the 1LF2 even had a PC=A instruction. Even if it didn't, it still could have supported RPL, albeit with a big performance penalty :

Code:

A=DAT0        A
AD0EX
C=DAT0        A
A=A+1         A
AD0EX
RSTK=C
RTN

instead of just

Code:

A=DAT0        A
D0=D0+        5
PC=(A)

If the 1LF2 had a PC=A instruction, then one could do

Code:

A=DAT0        A
AD0EX
C=DAT0        A
A=A+1         A
AD0EX
PC=C

which is still very slow, but saves one instruction

Jonathan