Nonpareil status

[brouhaha]

There's been a long-standing bug in Nonpareil, with use of memory on the HP-55 not working properly. I haven't looked at it since 2005, but it's been bugging me. I just discovered that Greg Sydney-Smith analyzed the problem and came up with a fix for his own simulator in 2018:

https://www.sydneysmith.com/wordpress/20...lator-bug/

I've updated Nonpareil and the 55 registers and statistics seem to work properly now.

It seems very odd that the 55 uses a mix of one-digit and two-digit addressing, distinguished by C[0]. The secondary ("dot") registers R.0 through R.9 are RAM addresses 0 through 9, and are addressed using BOTH methods at different points in the microcde. Apparently the RAM chip (1820-1393, possibly also the earlier 1820-0993) were designed to do both. Now I'm curious as to whether the 45, 46, 65, 70, and 81, which AFAIK do not use two-digit addressing, always select RAM with C[0] = 0. That's not something I'm going to study right now. Nonpareil implements this only for calculators which are defined (in the .ncd compressed XML file) with arch="Classic" and arch_variant="1", which is only the case for the 55.