755 MT, motherboard work in a 380 SFF case?

No it won't work at all for ANYTHING that you want to do.

The 380 uses DDR3 PC3-12800 • CL=11 • UNBUFFERED • NON-ECC • DDR3-1600 • 1.35V • 512MEG X 64 •

The 755 uses  DDR2 PC2-5300 • CL=5 • UNBUFFERED • NON-ECC • DDR2-667 • 1.8V • 128MEG X 64 •

The front panel and sensors and everything else is totally different.

thank you sir,

"He said he can use his old DDR2 sticks with the 755 motherboard."

This is not likely unless they are low density,  non ecc, non registered,

PC2 5300, single or dual rank, etc.

In addition he can buy the O755 front I/O assembly.

What he wants to do is use the 380 front I/O which is NOT compatible.

There is also a  thermal sensor on the 755 Desktop and SFF

It is in no way a water chicken install set and forget so respectfully I completely disagree.

And FINALLY " 755 MT motherboard work in an optiplex 380 sff case"

Thats not happening because it DOES NOT PHYSICALLY FIT into the SFF Case let alone line up with the holes on the case floor.  2 Slot vs 4 Slot motherboard.

The coup de grâce final nail in the coffin is the 380 power supply Connector is NOT compatible and the power supply is not 305W on the SFF which the MT motherboard Requires.

https://www.moddiy.com/products/Dell-980-960-780-760-PSU-24-Pin-to-Mini-24-Pin-Adapter-Cable-10cm.html?setCurrencyId=1

TINY 24 pin vs Regular

SFF VS MINI TOWER SIZE IS OBVIOUS AND NOT WORKING

problem solved