HP-33E Missing Pin on Memory Chip

[brouhaha]

(05-03-2024 02:20 AM)teenix Wrote:  I have one of these chips with the silver paint faded a bit and can almost see what looks like a standard serial number on it like xMxx-x00x. I cannot make out the x's.

I think the 33E (but not the 33C!) would normally have three memory chips (from my very old notes, not guaranteed):
* 1MA1-0004 _OR_ 1MA1-0204
* 1MA1-0003 _OR _ 1MA3-0002
* 00031-80008

For the 3xE series, the memory chip slots are fully interchangeable, so each memory chip can be in any position. For the 3xC series, the 1LB9 CMOS memory chip must be In the top position.

Note that the 40-pin chip includes the first 1Kx10 of ROM, which is why they're not fully interchangeable across all Spice models. There are three different ones, though each is known by both an 1818-nnnn and a 1MA4-nnnn part number.