HP-27S speed compared to HP-42S


I just received my HP-27S today. Really pleased to finally have this calculator, an early model assembled in USA and in mint condition.

I've always believed the processor was the same in 27S and 42S, but I wonder if it's clocked higher in the 27S?

I can definitely see a clear difference in execution speed just by entering 200! On the 27S the answer arrives almost instantaneously, but on my 42S it's about 1.1 s.

Edited: 5 June 2013, 10:36 a.m.


I don't have a 27S at hand but I know the 42S allows for real (i.e. non-integer) input for x! - maybe this explains the difference.



I know the 42S allows for real (i.e. non-integer) input for x! - maybe this explains the difference

It does not, GAMMA will do that. I guess the 27S uses always an approximation for the gamma function while the 42S does n-1 multiplications, which takes longer for large n. On my 32SII 200! takes about 1 second while 200.0000001! is computed almost instantly, same for GAMMA on the 42S. It appears the HP-27S has suppressed the plain multiplication algorithm for integer arguments, perhaps in order to save ROM space.


These Pioneers return the measured CPU strobe frequency in Hz during the self test.

The nominal speed of both is ~1MHz.

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