Prime number finder HP11C?

[jbhp55]

Hello Gerson,

that explains it!
I am not the happy owner of a 15c (LE), but I found to my surprise that the humble HP20S takes only 3 s. for the 999 - 1009 step, using virtually the same code. My 32SII is only very slightly faster (this I can understand in view of the processor). My fastest option is a 48G, which I haven't tried with an equivalent program, but a similar program takes roughly one second.
For the 17BII, I only have an equation which states whether or not a number is prime. It verifies 1009 a lot quicker than the 20S (10,007 in 2 s. on the 17BII, and 4 s. on the 20S). Apparently, the equation solver can use efficient algorithms internally.

Best regards,

Jaap.