HP-41 Math/Stat Pac?


I've seen a "Math/Stat Pac" ROM included in various 41C* auctions. This module is listed in a 1987 HP calc accessories brochure, but not in the HP-41CV accessories flyer from 1982. The Pac's manual has not been scanned for the MoHPC CD set, to my knowledge.

Q: Does the Mat/Stat Pac include *all* the functionality comprised by the "Math I" and "Stat I" Pacs available in the early '80s? (I have both of these, with manuals.)




yes !


as thibaut.be already wrote, you'll have the whole functionality of both modules.
You can imagine it as if two modules were in the same port at the same time. You could even make your own Math/Stat pac by soldering both ROM pcb's into one module case;-)



The MATH/STAT PAC for the HP-41 comes with the Math Pac Manual, The Stat Pac Manual, and a card 00041-9056 "ABOUT THIS PAC AND ITS MANUALS" that says there is no seperate manual, just use the two manuals,

You can not just solder a MATH PAC and a STAT PAC together, you would get a port conflict. You can solder one application ROM with a system addressed ROM, such as TIME MODULE, EXTENDED FUCTIONS/EXTENDED MEMORY, EXTENDED MEMORY, QUAD MEMORY, HP-IL, etc.

See the BUTCHER'S BLOCK articles by David (Ebras) White in the PPC Journals for some great write-ups on module doubling and module tripling.


Of course you're right regarding putting (or better not) the ROMs together.

I simply forgot these port-coding mechanics while writing the article.

Maybe too long ago since I fiddled with modules;-)




Actually, although the Math/Stat Pac contains the same code as the separate math pac and stat pac, you can't just solder the 2 PCBs together to make the combined pack. To understand why not, you have to know something about the HP41 memory layout. The Nut CPU can address 64K words of ROM. By convention, this is divided up into 16 4K pages. The first 8 pages (0-7) are used for 'system' functions -- the HP41 firmware itself, printer ROM, HPIL ROM, Time module ROM and service module.
The top 8 pages are allocated to the I/O ports, 2 pages to a port. Note that strictly this is only a convention (which is why you can put the HPIL ROM into a port, even though it needs to fit into one of the system pages). Devices plugged into the port are responsible for decoding the full 16 bit address and deciding if they should respond or not.
To help them do this, there are 2 pins on each port that are wired differently (either to the +ve supply line or not connected) on each port. So a module can tell which port it is plugged into.
Most plug-in ROMs (apart from special ones, like printer or HPIL) do use these lines, and then the ROM appears in one of the 2 pages allocated to that port. That way you can plug any module into any port.
Now, 2 pages for each port is 8K of memory. Most of the early modules were only 4K long _and appeared in the lower page of the 2 allocated to the port they were plugged into_. The math pac and stat pac both do. Therefoe if you do manage to wire them both into the same port, you'll just get 2 ROMs conflicting in the lower page, so nothing will work. The genuine Math/Stat pac contains an 8K ROM which puts the Math part and the Stat part in different pages, as you might expect. There is no way to fiddle this -- there is no way to move a ROM between the low and high pages of a given port.
You can make a ROM (or other module) appear to be in a port other than the one it's physically plugged into (by miswiring the 2 select lines), which is how you can double up the Extended Memory modules. They use _one_ of the 2 select lines to decide where to appear in the (separate) RAM memory map, so by soldering 2 of those toghter and fiddling the select lines, you can end up with a double-capacity module that fits into one port (and, indeed, which can share a port with a ROM module).
Oh, yes, a couple of exceptions. A few 4K modules occupy the upper page only, and these can be combined with a 'normal' 4K module in the same port. ZenROM is one such. And the card reader ROM is hardwired to appear in page E (lower page allocated to port 4). OK, the card reader will only physically fit in port 4, so it doesn't really matter, but if you did manage to wire it into another port you'd discover that the ROM (which, in this device is a normal 8 pin DIL chip) ignores the select lines.


You should not put the Card RDR ROM to an other page than E.
The 2-word GTO/XEQ (on carry/no carry) are "hard coded", not port dependent.


BTW, this list was obviously scaned for email addresses as I received spam to "Mike (Stgt)". The addition 'Stgt' I only use on this list to show my location. M.


Well, the physical ROM in a 41 card reader is an 8 pin chip that will _always_ appear in page E. That chip has no pins to select which page it would appear in.
I suppose the only way you could move the ROM software to another page would be by copying it into an MLDL box. And I guess you're telling me that if you do this it won't run. Interesting.


Not only in an MLDL it would fail, in an SW emulation too.
Well, I never tried it anyway :-)

If you look the firmware listings (VASM, MCode) you see at once, that far jumps (Go To/Execute - on Carry/on No Carry) are normaly coded "port independent" with 3 10-bit words (by calling a appropriate Main Frame routine with a relative address where to go realy). All 2-word GTO/XEQ in the Card RDR ROM go directly on page E.


BTW - who is reading along VASM listings anyway <VBG>


I believe it does. I would like copies of your math and stat manuals however since I have lost mine. Are you willing to help? jbreda@massmed.org


Are you aware of the Museum CD-ROM set? It includes scans of manuals for many HP calculators and accessories including the 41C Math Pac and Stat Pac. Here is a page with a list of the contents:


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