The only person who can fully answer that outside of The Woz was my old friend Dr. Levinson, who died in '09. So unfortunate, he was a wealth of Apple II Info. So I'll need to activate some very old memory neurons here...
The chip with the White Sticker is a 512B to 1KB Flash PROM (P6), 4bits wide and the other 4 bits (for 8 bits to be used by the 6502) is on the other PROM (P4). They are sensitive to static, voltage spikes, shorts and anything that would suddenly rise the volts/amps inside the Apple and can be accidently erased. This card is the 5.25 drive card and not a 3.5, and I as wondering why is there 2 drive cards in it. If they put a 3.5 drive to that, it would have killed the card.
This is known - the 5.25 and 3.5 are virtually the same except for bigger PROMs on the board to figure out 3.5 geometry. There is an extra voltage line coming from the card to handle the little motor for Disk Ejection which is grounded on the 5.25 drive. This is why plugging in 5.25 to it would kill the card and the drive and why plugging a 3.5 into a 5.25 card would kill the card.
Incidentally, the IWM (Integrated Wozinak Machine) and the SWIM (Super Integrated Wozinak Machine) chips used in Macs are from these very same cards but with a different program in the PROM. So if you can imagine those cards on a chip, you get the IWM/SIWM.
Warning: This is also why you can not use a Apple IIGS 3.5 floppy on a Mac - both the wires and the drive board inside are different. Using it will blow out your IWM/SIWM Chip and/or the drive. You can recycle the mechanicals from a Apple IIGS 3.5 to fix a Mac 800K floppy (and visa versa) but not the electronics.
The chip with the White Sticker is a 512B to 1KB Flash PROM (P6), 4bits wide and the other 4 bits (for 8 bits to be used by the 6502) is on the other PROM (P4). They are sensitive to static, voltage spikes, shorts and anything that would suddenly rise the volts/amps inside the Apple and can be accidently erased. This card is the 5.25 drive card and not a 3.5, and I as wondering why is there 2 drive cards in it. If they put a 3.5 drive to that, it would have killed the card.
This is known - the 5.25 and 3.5 are virtually the same except for bigger PROMs on the board to figure out 3.5 geometry. There is an extra voltage line coming from the card to handle the little motor for Disk Ejection which is grounded on the 5.25 drive. This is why plugging in 5.25 to it would kill the card and the drive and why plugging a 3.5 into a 5.25 card would kill the card.
Incidentally, the IWM (Integrated Wozinak Machine) and the SWIM (Super Integrated Wozinak Machine) chips used in Macs are from these very same cards but with a different program in the PROM. So if you can imagine those cards on a chip, you get the IWM/SIWM.
Warning: This is also why you can not use a Apple IIGS 3.5 floppy on a Mac - both the wires and the drive board inside are different. Using it will blow out your IWM/SIWM Chip and/or the drive. You can recycle the mechanicals from a Apple IIGS 3.5 to fix a Mac 800K floppy (and visa versa) but not the electronics.