71 & 75 Math ROMs, Series 80 Matrix ROM

[J-F Garnier]

(05-21-2018 04:08 PM)J-F Garnier Wrote:  

Quote:... the HP-71B's is a 32Kb ROM and the HP-75C's is a 16 Kb one. I don't think that Capricorn assembly language is 2 times more space-efficient than Saturn assembly language so I don't think that it could fit in 16 Kb what it takes 32 Kb in the HP-71B.

This is surprising for me too. Even if the 71 Math LEX is only 27 kB long (the rest of the ROM is filled with 0), it makes a big difference of code size.

I found a possible explanation on the reason of the much bigger size of the 71 Math ROM, compared to the 75 version, in the article about the 71 Math ROM in the HP Journal, July 1984:
"One major improvement in the matrix operations of the
Math Pac over its BASIC language predecessors is in the
area of speed. This improvement was made possible
through the use of direct pointer manipulation into arrays,
rather than accessing array elements by their indexes.
...
This speed improvement came at the expense of more ROM space.
However, this was not a major constraint, as was the case in the
HP-85 Matrix ROM and HP-75 Math Pac."

So the 71 team considered that 32 kB was plenty of room, they used it to optimize the code for speed but didn't try to fill all the available space completely.

J-F