[41CL WARP] XEQ+ oddness

[Ángel Martin]

Thanks to both for the testing, so now we're on the same page and you two are seeing the same problem so there's got to be something intrinsically wrong in there. I've configured my CL using the same ports and the issue also happens - finally - on my system. I typically plug the PWRX in page#7, I guess that's why this didn't ever come up for me.

Looking at the choice of pages I believe the standard bank-switching behavior is the root cause of the problem. Notice that both pages #A and #B will bank-switch together, i.e. it happens at the PORT level. This is so that dual-page modules (like the HP41 Advantage) work OK during the bank-switched calls.

So what happens when both the PWRX and the WARP are in the same "port" (pages #A and #B) is that they'll both switch banks together. This is bad because the WARP code will instruct the PWRX to switch banks looking for auxiliary FATS in it. When it does, the execution returns to the WARP to read the aux-FAT contents - but alas, WARP is also in a different bank so the execution returns to la-la-land, and hence the screw-up/

The solution: never plug the WARP together (in a port) with another single-page, bank-switched module such as PWRX, OSX3, 16CS... and the problem won't occur.

Note that two-page bank-switched modules (like SandMath, SandMatrix, 41Z, etc.) could also show this problem if you plug them in a port-straddled configuration (upper page of lower port and lower page of upper port). This of course is not possible in the real machine or V41/41X but on the CL the flexibility is total so it's possible to do it.

So the proof is in the pudding: simply plug the WARP in a port without other B-S module and try again. I'd strongly recommend using page#7 for either PWRX or WARP, assuming of course that no HP-IL is needed.

And the verdict is...