71 & 75 Math ROMs, Series 80 Matrix ROM

[rprosperi]

(05-28-2018 02:04 PM)J-F Garnier Wrote:  

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

Nice find J-F, thanks for sharing this. It explains the mystery of why so much space was left empty... the 71B MATH ROM is really is a 16KB ROM that grew to 27KB as a result of Saturn code optimization for speed, rather than a 32KB ROM that they chose not to fill.

I also recall reading (somewhere...?) that much of the Math ROM was initially proposed to be included in the system ROM, but was later moved to an accessory module when the proverbial ROM 'was full'. Given how much ROM space is required for these functions, this seems unlikely and I suppose could just be speculation, that was repeated over an over, and eventually became historical lore over the years.