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Joe Horn · (This post was last modified: 01-15-2017 04:32 AM by Joe Horn.)

(01-14-2017 06:34 AM)teenix Wrote:
(01-14-2017 05:50 AM)Joe Horn Wrote: Tony's '97 emulator is so authentic that pressing "Sigma-minus, x-bar, %CH" makes it crash, just like the real '97!

Hi Joe,

Nothing like trying to be authentic ;-)

I wasn't aware of these problems.

I cannot get these keys to malfunction, is there some special circumstances where these errors occur? I might be able to figure out the microcode problem.

cheers

Tony

Oh no, please don't "fix" this! It's a bug in the original '67 and '97 which really should be kept. Here's what happens: After turning on, pressing Sigma-Minus followed by X-bar puts a negative zero in stack register Y. This can only be seen by executing the STK command on the '67 (or by executing PRINT STACK on a *real* '97 or on a very good emulator). If %CH is executed with that negative zero in Y, the poor machine attempts to divide by zero (the negative sign makes it think it's not zero) and of course it crashes.

Some '97 emulators (e.g. "RPN-97 Pro" from cuveesoft.ch) generate an "Error" when division by negative zero is attempted. I personally dislike that, since IMHO the best emulators act exactly like the original calculators, bugs and all.