Discount Rate

[Thomas Klemm]

Comparing the code in HP Journal to the US patent, I noticed something slightly interesting:
In the US patent DOWN ROTATE is used twice in several places, while in HP Journal a JSB DR2 is used.

Here are the corresponding code snippets for comparison:

US Patent

Code:

L3222:   .....1...1      → L3004               JSB XTY
L3223:   11..1.1...                            DOWN ROTATE
L3224:   .1..1.1...                            C → STACK
L3225:   111..1.1.1      → L3345               JSB MPY
L3226:   ..1...111.                            B → C[W]
L3227:   11..1.1...                            DOWN ROTATE
L3230:   11..1.1...                            DOWN ROTATE
L3231:   111...11.1      → L3343               JSB DIV
L3232:   11..1.1...                            DOWN ROTATE
L3233:   11..1.1...                            DOWN ROTATE
L3234:   .1...11..1      → L3106               JSB ONE
L3235:   .11.1.1..1      → L3152               JSB SUB
L3236:   1.1.1.1...                            M → C[W]
L3237:   111...11.1      → L3343               JSB DIV
L3240:   11..1.1...                            DOWN ROTATE
L3241:   11..1.1...                            DOWN ROTATE
L3242:   .11.1.1..1      → L3152               JSB SUB

HP Journal

Code:

L3224:   .....1...1      → L3004               JSB XTY
L3225:   11..1.1...                            DOWN ROTATE
L3226:   .1..1.1...                            C → STACK
L3227:   111..1...1      → L3344               JSB MPY
L3230:   ..1...111.                            B → C[W]
L3231:   ...1.1.1.1      → L3025               JSB DR2
L3232:   111...11.1      → L3343               JSB DIV
L3233:   ...1.1.1.1      → L3025               JSB DR2
L3234:   .1...11..1      → L3106               JSB ONE
L3235:   .11.1.1..1      → L3152               JSB SUB
L3236:   1.1.1.1...                            M → C[W]
L3237:   111...11.1      → L3343               JSB DIV
L3240:   ...1.1.1.1      → L3025               JSB DR2
L3241:   .11.1.1..1      → L3152               JSB SUB

While I couldn't find the DR2 label in ROM 3 of the US patent, I was able to find similar code in ROM 5:

Code:

L5071:   11..1.1...                    DOWN3 : DOWN ROTATE
L5072:   11..1.1...                    DOWN2 : DOWN ROTATE
L5073:   11..1.1...                            DOWN ROTATE
L5074:   ....11....                            RETURN

Both DOWN2 and DOWN3 are used in this ROM.

I wasn't aware of several ROM versions of the HP-80.

Based on Bernhard's statement I assume that the code from the US patent is used in the HP-80:

Quote:I compared my HP-80 ROM code and found, that is was correct.

While some of the ROMs can be downloaded, the HP-80 unfortunately is missing.
Therefore I can not verify that.

If anyone can shed some light on the subject I would be very grateful.