WIP: 16C firmware hack for more memory

[brouhaha]

(01-22-2023 09:08 AM)dmh Wrote:  I've been wondering about synthetic programming on the other Voyagers that also exhibit the rotate X functionality like on the 15C.

Any chance you've looked or seen anything that might provide insight as to whether this is possible and how (eg alpha display)?

The Voyager ON-key14 (y^x, D, PMT) combination causes a hard reset of the Nut processor resulting in an abrupt jump of 22 bit cycles in the Nut. Lesser known is that it does that to all of the Nut's internal 56-bit data registers, and also some other internal non-56-bit registers including the status register. That's why under some conditions, performing that shift operation turns on or off complex mode, WITHOUT allocating or deallocating the complex stack. There are probably other side effects that haven't been characterized.

The main reason the shift is useful for 15C synthetics is that it allows creation of invalid matrix descriptors that point to other places in RAM, such as the pool.

Since none of the other Voyager models have any similar pointer mechanisms, I don't think synthetic programming on the other models is practical with or without the use of ON-D.

The work I'm doing in on modifying the firmware, which is difficult on the real Voyager hardware, but perhaps not too difficult on the ARM-based models from both HP and SwissMicros. That potentially allows us to do anything the hardware is capable of. On the SwissMicros calculators, in principle we could hack the calculator firmware to allow individual pixel control of the LCD, and use of the beeper and real time clock. While this is technically possible, it's not currently on my (near-infinite) to-do list.

I do want to figure out how the Voyager firmware is stored inside the SwissMicros firmware, so that I can test my hacks to the Voyager firmware on them. I haven't yet done anything about that. From what I hear, in early versions of SwissMicros firmware that was easier than in newer versions, but I haven't confirmed that myself.

Alternatively, I could just write my own Nut simulation code etc. to run on the SwissMicros hardware, without need for their proprietary firmware.