Question about HP71B Variable Names

[J-F Garnier]

(01-19-2021 01:48 AM)Garth Wilson Wrote:  

Quote:Another concern is speed, the HP-71B is quite a slow beast (even back at the time, as compared to the HP-75C or the HP-85, say, about 5x slower)

Do you have any speed comparisons, for different types of benchmarks? I know it was slower for something like a FOR...NEXT loop (probably because the 75 had a wider data bus), but I think the 71 was much, much faster in math that involved the math module. The two computers had approximately the same clock speed, but the 71 could address eight times as much memory (which was great for when I had 128KB arrays plus all my programs in RAM), had a better BASIC, (I think) bigger registers (64-bit, and I can't find the 75's register size but I think it's 8-bit) [...]

You can have a look at this benchmark with many machines. Results for the 71 and 75:
- 46.2 HP-75C Basic / Fast Integer
- 2:33 HP-71B Basic / Ver.1BBBB
so a ratio of 3, mainly due to the "Fast Integer Processing" of the 75.

For pure math non-integer operations, the ratio is about 2 still in favour of the 75. Reason is that the 75 CPU is internally a 8-bit machine whereas the 71 is a 4-bit one requiring twice the number of clock cycles for the same operation.

However, the designers of the HP-71 Math ROM optimized the code, especially the matrix operations, to get acceptable performances, basically using pointers instead of indexes to access arrays (in C style: using *a instead of a[i]). This reduced the pointer calculation overhead but still the HP-71 is not a fast math machine.

J-F