4K HP 67 Games rom attached for testing

[Dieter]

(11-02-2016 09:49 PM)Gene Wrote:  Gene: At a first glance, it does not appear to be the same. In the original, LBL 1 recalls 10 and adds it to memory 5. Robert's port adds 1 to memory 5 for a alglog detection using ISG and after the scan, multiplies the total by 10. That is fine, but the CLX is always skipped by the ISG (problem because we don't have an INCrement instruction.

Now look at the original '67 code. Here a subroutine is called that adds 10, but on return this "10" still is in X on the stack (!). Then the CLX commands clear X, which may be this 10 or the value of R20/21/22..., depending on whether the increment routine was called or not. Looks a bit strange to me.

(11-02-2016 09:49 PM)Gene Wrote:  A fix is to change the instruction after the ISG 05 to a true NOP and then the CLX. That will add 4 ? bytes, but that's ok we have them to spare.

This should work if the code is supposed to increment R05 each time the input matches R20, R21, R22... etc. If this is what the routine should do the '67 version is buggy as well, and the ST+5 commands in line 147 and 151 should be followed by a RDN. But maybe there is another very clever reason why they are not, and I am simply unable to see it. #-)

Dieter