All bugs are described in detail in the book „Extend your HP-41“ by W. A. C. Mier-Jędrzejowicz.
HP-41 Bugs
| No. | Description | Reference |
|---|---|---|
| #1 | Early machines did not save X into L when Σ+ and Σ- were done. Example: 41 Σ+ LastX, if you do not see 41 bug is present. | |
| #2 | Early machines allowed RCL IND nn and STO IND nn when nn was outside the memory range. Example: Master Clear, SIZE 000, 999, ENTER, π, STO IND Y, CLST, 999, RCL IND X. If π is displayed, bug is present and the question is where is it being stored if the machine doesn’t have any data registers? | |
| #3 | Early machines allowed SF,CF,FS?C, and FC?C IND nn with nn any number (but not a stack register) 0 to 55. Example: 49, STO OO, SF IND 00. If you see the BAT indicator bug is present. | |
| #4 | Early models compute the SIN of small angles incorrectly. Example: 1 EEX CHS 99 SIN. If the result is 0.174532925 bug is present. | |
| #5 | CLP would only clear 1089 program lines. | |
| #6 | -67A/-97A programs that contain combinations of number entry, EEX, and CHS do not translate correctly. Example: EEX CHS 7 CHS 5 translates to E-7-5 instead of 1E-7 -5. | |
| #7 | The second nybble of the seventh byte of Alpha is copied along with the first six bytes during an ASTO. | |
| #8 | Early machines do not decompile programs if they are turned off during PRGM mode. | |
| #9 | Executing CAT 1 while in PRGM mode, then interrupting it with R/S causes step labelling oddities. | |
| #10 | If flag 25 is set and MEAN or SDEV causes an overflow, some flags can be altered. | |
| #11 | If a program at the end of CAT 1 is replaced or deleted, a return to that program will return into the new program or off-program memory. | |
| #12 | On early models, the function LN(1+X) gives wrong answers for values of X between -.9990234374 and -1.00. | |
| #13 | On early models, the operation (.1)^-43 gives an answer of 9.999999999E42 instead of 1E43. |
HP-41 ROM Versions
| Version | Date Codes | Comments |
|---|---|---|
| DDD | see here | |
| DDE | 1926-1940 | all bugs |
| FDE | 1936-1952 | #3 removed |
| FEE | 1951-2034 | #1,#2,#4 removed |
| GFF | 2035-84?? | #5,#7,#8 removed first -41CV version |
| HFF | 84??-present | current -41CV version |
| NFL | 2329-present | current -41CX version |