Can someone tell me which Clear and Set chips I need for...

[modessitt]

SP831 and SP1271?  I'm hoping they use the same, but am not optimistic.  I looked at the SP & ST lists, but it's hard to read if your not a slot expert.

Also, I just looked at two different slots that both had an SP1271 chip.  Does that sound right?  I'm guessing the way it plays and pays out is the same?

[knagl]

The clear chip you use on an IGT S+ is typically the same for any SP chip -- the clear chip blasts the data on the EEPROM that is soldered into the (typically) non-removable motherboard, and gets it ready to accept new data.  Typically a clear chip is not needed, however, and should only be used as a last resort (please see the sticky topic here in the S+ section).  You generally don't even need a clear chip when switching between different game types.

SP831 uses SET026.  SP1271 can use SET088/89/90/91/101/102/116/121 , so you will need two different set chips to configure both of those SP chips.

As far as your two different slots that both have SP1271 in them, that's entirely possible.  Think of the SP chip as the "operating system" for the machine, and the SS chip is the software that is specific to that game theme (the paytable for the particular game).  The SP1271 can operate any game type of 0, 1, 4, 5, or 19.  A list of game types can be found here.  Many games are type 0 games (no nudging or respins).  The IGT Game Bible indicates each game type for a specific theme name.  (ie. Double Diamond is a type 0 game, and Double Jackpot Haywire is a type 2 game)

[StatFreak]

...
SP831 uses SET026.  SP1271 can use SET088/89/90/91/101/102/116/121 , so you will need two different set chips to configure both of those SP chips.
...

I beg to differ. You can use the SET026 to turn on the DBV and set the denomination on the SP1271 with no problems. You will only need one of the newer set chips if you want to set up progressives.

[modessitt]

The clear chip you use on an IGT S+ is typically the same for any SP chip -- the clear chip blasts the data on the EEPROM that is soldered into the (typically) non-removable motherboard, and gets it ready to accept new data.  Typically a clear chip is not needed, however, and should only be used as a last resort (please see the sticky topic here in the S+ section).  You generally don't even need a clear chip when switching between different game types.

Thanks, but all three slots have dead batteries (been sitting for over a year) and despite others' successes, I've never been able to clear a 61 error after a battery replacement without doing the Clear Chip.

[knagl]

I beg to differ. You can use the SET026 to turn on the DBV and set the denomination on the SP1271 with no problems.

I defer to your real-world usage of the SP1271 -- I was just going off the info from the PAR sheet.