HP-80 CHS Exponent Curiosity
#1

My one and only classic HP is an HP-80, like many with the 1247... serial number but the ROM chip shows a date of 1/73.

It exhibits a strage characteristic when in exponential display mode with a number less than 1, and CHS is pressed. Instead of only inserting a negative sign in the left-most position, it also changes the exponential value to -99.

Toggling CHS leaves the exponential value at -99 but toggles the left-most negative sign as expected. However, pressing SAVE resets the exponential to the original value, switching back to decimal display shows the correct value and calculations are correct even when the exponential value shows -99.

For an example keystrokes and display:

Power on " 0.00 "
.1 SAVE " 0.10 "
Shift 7 " 1. -01"
CHS "-1. -99"
Shift 2 "-0.10 "

So it seems the CHS induced exponential -99 display is just a display curiosity, but I cannot find any reference to it anywhere. Is this something other people have seen on the HP-80?

Kind regards, MAX

#2

HP's original serial number system used the four digit date code as the first week of production of machines of a particular revision level, rather than the week a particular unit was actually manufactured. For calculators the production volume quickly ramped to a high enough rate to make that scheme unusable, so at some point before 1976, for calculators only, the scheme was changed to have the date code reflect the actual production week, without regard to the revision level of the product.

#3

I don't remember coming across this before, but my early HP-80 and later one (with a "Hewlett Packard 80" nameplate on the front) both exhibit this same display problem. The HP-81 I have doesn't have this issue, but the display system is somewhat different.

#4

I'm fairly certain that it's a firmware bug, and they probably fixed it before releasing the HP-81. It's possible that late production HP-80 units that used the quad ROMs (two HP-45/55/70 style DIPs rather than a hybrid) might have it fixed, but I don't have such a unit to try.

#5

Thanks guys for the feedback. Maybe it should be added under the 'Bugs' section?



Possibly Related Threads…
Thread Author Replies Views Last Post
  HP Prime CAS curiosity bluesun08 11 4,998 12-10-2013, 01:03 PM
Last Post: Han
  HP Prime Matrices curiosity bluesun08 0 1,550 12-09-2013, 06:44 PM
Last Post: bluesun08
  HP-80 History, Design and Interesting Facts BShoring 1 1,392 11-30-2013, 08:50 AM
Last Post: Xavier A. (Brazil)
  [HP Prime] Using n-root symbol and exponent problem uklo 7 3,005 11-11-2013, 01:39 AM
Last Post: Alberto Candel
  Another Prime curiosity Michael de Estrada 0 997 11-05-2013, 11:52 AM
Last Post: Michael de Estrada
  HP-80 Teardown with pictures Max Stone 10 3,987 10-24-2013, 09:10 PM
Last Post: Walter B
  HP 80 emulator Olivier De Smet 4 1,930 09-02-2013, 09:39 AM
Last Post: Vincent Weber
  HP 35 ... 80 Olivier De Smet 6 2,569 08-29-2013, 07:25 AM
Last Post: Olivier De Smet
  WP34s curiosity... Stephan Matthys 7 2,515 08-24-2013, 10:40 PM
Last Post: Dale Reed
  HP-34C Curiosity Matt Agajanian 7 2,822 08-23-2013, 06:02 PM
Last Post: Stephan Matthys

Forum Jump: