Bug in MATH ROM of the TI-95

[Namir]

I have been tinkering with the TI-95 and its MATH and STAT ROMs. I discovered that the Newtons Root method (option NTN in option ZRO) has a bug that causes the solution FOR ANY FUNCTION to jump to huge numbers and then overflow. I tested my fx(x)=exp(x)-3*x^2 and fx(x)=x^2-5*x+6 functions and both bombed out. I inserted a pause (PAU) command in my function code to trace the values used by NTN and found that it does the following:

1) Evaluate fx at you initial guess (call it X).
2) Evaluate fx at X plus a small increment.
3) Evaluate fx at X minus a small increment.
4) Evaluate fx at a large number.
5) Repeat step 4 with different large numbers until the calculations overflow.

I also noticed that the TI-95 emulator by HrastProgrammer has the same bug in his port of the MATH ROM! I guess his ported the binary image of the MATH ROM.

Anyone else out there has seen this bug?

The Bisection method in the MATH ROM works fine!

Namir