Just to set the information baseline ...
About NUT CPU architecture:
- CPU is able to directly address 64K word (10 bits) ROM or RAM
- the 64K address space is divided into 16 pages of 4K
- each 4K page can be bank switched (4 banked pages max, for a theoretical total memory memory of 256K)
- CPU native instruction is machine code (MCode) [not RPN]
- CPU native memory is 10 bits word [not registers]
List of system peripherals:
- RAM Registers (internal and/or plug in modules, including main and extended memory)
- Display (internal)
- Card Reader (82104A)
- Wand (82153A)
- Thermal Printer (82143A)
- HP-IL (82160A)
- Timer (82182A)
- Infra-Red (82242A)
About HP-41 Operating System (limited enumeration)
- 41OS C/CV size is 12K and is hardwired to pages 0, 1, 2
- 41OS CX size is 24K and is hardwired to pages 0, 1, 2, 3, 5 (Bank 0 & 1)
- 41OS implement an RPN language interpreter (aka FOCAL)
- 41OS store RPN data and programs into RAM registers (peripheral)
About RAM Registers (peripheral)
- 1 x RAM register has 56 bits (or 7 bytes, that size was directed by the CPU ALU register size of 56 bits)
- 1 x RAM register chip has 16 x RAM registers (or 112 bytes)
- 1 x Memory Module (82106A) has 4 x RAM register chips (64 registers or 448 bytes) [mapped to main memory space]
- 1 x Quad Memory Module (82710A) has 16 x RAM register chips (256 registers or 1792 bytes) [mapped to main memory space]
- 1 x X-Functions/Memory module (82180A) has 8 x RAM register chips (128 registers or 896 bytes, 4 registers are used for memory management) [mapped to extended memory spaces]
- 1 x X-Memory module (82181A) has 16 x RAM register chips (256 registers or 1792 bytes but only 239 registers are usable) [mapped to extended memory spaces]
About 41 Models (SM = Status Memory, MM = Main Memory, XM = eXtended Memory)
- HP-41C has 5 x RAM registers chip inside (1 for status and 4 mapped to main memory) [SM: 16 registers / MM:64 registers / XM: 0 registers]
- HP-41CV has 17 x RAM registers chip inside (1 for status and 20 mapped to main memory) [SM: 16 registers / MM:320 registers / XM: 0 registers]
- HP-41CX has 25 x RAM registers chip inside (1 for status, 20 mapped to main memory and 8 mapped to extended memory) [SM: 16 registers / MM:320 registers / XM: 128 registers]
See:
HP-41 Memory Map
Answers to your questions will follow later.
Sylvain