Re: HP-41: Question on Halfnut vs Fullnut Message #4 Posted by Tony Duell (UK) on 30 Oct 2002, 7:49 p.m., in response to message #1 by Juergen Rodenkirchen (GER)
The Fullnuts have a separate CPU/logic board. The keyboard PCB in a Fullnut is just the keyswitches, and the display driver hybrid is soldered to one edge of this PCB. The display driver hybrid is just the display driver. The CPU board contains the CPU chip, ROM, RAM, PSU chip, timer chip (in a CX), and so on.
The halfnuts have everything on one PCB. The CPU is a surface-mount decive solderd to the back of te PCB, under the keybaord. The display driver hybrid now also contains the ROM, RAM and PSU circuits.
Halfnut CXs have a little hybrid PCB mounted across the back of the main PCB, over the CPU. It cotnains the extra ROM, exteded RAM, and timer circuits. Alas, the ROM code in the dispay driver is different between the CV and CX, so you can't upgrade a CV just by adding the extra PCB.
AFAIK, no fullnut was ever converted into a halfnut by HP. To do that you'd have to replace the entire top case (including the PCBs). Just about all that's common between the fullnut and halfnut models is the bottom case and I/O assembly (the flexible PCB that connects to the modules and the battery pack.
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