HP 71B Pocket Computer from 1984 

Yeah I find HP calculator collectors are polarised by the 71B, there are some big fans but also many who are ambivalent like yourself.

Curious what your other favourites are Eddie?

Thanks very much

Wow great find!

Thanks for the correction.

Sorry but you are totally wrong. Saturn CPU is 4-bit processor because its ALU is 4-bit and its data paths are 4-bits size. Register size of some registers doesn't define cpu bit size. If it was 64-bit internally, it would need 64-bit ALU and 64-bit internall data path, none of these exist internally. When you need to add two 64-bit internal register it takes like 8 more time than to add 8-bit, or 16 more than 4-bit size. The same for move and logical operations between registers. Even when in same Saturn versions it is connected to a "standard" 8-bit external memory, tha is divided in 4-bit nibbles beforse entering Saturn core.

@@CalculatorCulture That is totally wrong. Saturn CPU (or its later derivatives used in a lot of old good HP calculators, for example on marvellous HP-48 series; these were pocket computers, like HP-71b, not only calculators¹) has 64-bit data registers, 20-bit address registers and Program Counter (in fact it can linearly address 1 Meganibble memory, i.e. 512 Kbytes) ***BUT*** it is a 4-bit CPU: internal data bus and ALU (arithmetic-logic unit) are 4-bit wide. If you do an operation, be it move, arithmetic or logic, on 64-bit registers it takes like 16 more times than doing it only in 4-bit size, or 8 more times than doing it on 8-bit size. In this CPU you can do those ALU operations from only one nibble (a nibble is 4-bit data size) up to 16 nibbles (there is a lot of options to do so, it support variable data width). If you do it on more than a nibble it is done internally in a chained way, one nibble each time. If you would use an HP 48 you would see when you execute MEM command to see how much memory is free in bytes, it can answer with an integer number or a fractional number (always ending in .5 in decimal format if it is not integer) because processor its 4-bit size memory is accessed and organized in 4-bit size. For example a program or object could weight 80.5 bytes, i.e. 161 nibbles (80 byes * 2 + 1). Register size is a must for saying a processor is x-bit size, i.e. if a processor is x-bit it needs at least registers of that x size. But registers size doesn't define processor bit size. ALU and internal data bus define that point because ALU and internal data bus determine what can be done as a whole in one step (a step can take a few clock cicles in most old processors). Finally considering a CPU is x-bit size is a marketing and habit practice, not a scientific-exact one. For example Zilog Z80 is 8-bit because it was marketed that way and all people considere it is 8-bits CPU (we continue doing so); its internal bus is 8-bit wide (so on for external), it has 8-bit registers and can use some 16-bits registers but when it operate on them it takes like double time (two passes, so no 16-bit operation but 2 8-bit chained operations). Surprising a few years ago a lot of us learned Z80 ALU was 4-bit wide. I think in 80's near all of us were thinking its ALU was 8-bit wide, but it wasn't. ¹: Difference between a programmable calculator and a personal computer is that calculator is limited (by internal OS+software) to a calculator environment you can't escape from, while on a computer you can escape from those limitations and your only limit is the hardware itself. HP 48 can run machine code programs at will (and SYSEVAL command let you do machine code), doing all that hardware can do. On some BASIC language calculators there are POKE and CALL/SYS commands to call machine code programs, so in those you can't scape from calculator limitations (being then a real personal computer), but on others you can't secape from that calculator environment.

I used a BASIC program called makelex that prompts for hex codes and creates a lex file for you. holyjoe.org/HP71/lexfiles/MAKELEX.txt

I don’t believe so. You may want to check out Alex Garzas DIY kits for the HP 15C, 16C and 41C… www.tindie.com/products/hobbystone/px-15c-an-hp15c-emulator/

😂

Okay, but I’m not sure specially what you are referring to in this particular video. I do use the word ROM a number of times talking about the modules you could plug into the 71B. Are you referring to that or something else?

Maybe what you are saying is in other videos I use the word “ROM” fairly loosely to mean any memory the user cannot change, eg. where firmware or OS code is stored. Whereas sometimes from a hardware point of view this memory is updatable and not in ROM chips?

For someone complaining about referring to a variety of EEPROMs (notice the ROM in there) as ROM, this sure has some unclear assumption about what CMOS means. Fun side note, my Toshiba T1000 is equipped with two SSDs, one of which is truly ROM, and the other is SRAM (almost certain that's CMOS, like most logic including the CPU). Nothing prevents building a ROM with CMOS, e.g. KM23C32000C. Perhaps you think CMOS means calendar chips, as PCs commonly refer to them as such? They use CMOS for power efficiency, as the only battery powered section of the computer. Fully battery powered computers like the T1000 or pocket computers would use CMOS SRAM for the same reason, and often power the entire RAM in lieu of adding a separate storage device.