=== Internal details of the chip ===
* From [https://scarybeastsecurity.blogspothackaday.com/20202012/1108/reverse13/taking-engineeringa-forgottenlook-at-1970s.html The decapped photos of Intel 8271, NEC D765 and Intel 8272 chips-ics/#comment-734991 a comment in the hackaday website] prove that : "NEC D765 uPD765 Floppy Disk Controller: Internally this is a microcoded part with a primative controller of NEC’s own design. Testing microcode embedded in a part can be troublesome. The uPD765 had a few extra gates associated with the DMA Request and Intel 8272 chips are identicalDMA Ack pins. Presenting a certain illegal combination here places the part into a “test” mode and allows the sequencer microcode to be output on the normal Data pins. The sequencer microcode is responsible for high level commands such as Read Track, Recalibrate, Format Track, or Write Data. There is a similar test mode for the nano-code array which serializes data at the floppy disk head."
*NEC uPD765 (or just D765) is exactly the same chip as the 8272. NEC and Intel cross-licensed a bunch of IP back in the day. [https://forum.vcfed.org/index.php?threads/8272-fdc-to-8-drive-connections.45816/#post-557651 Source]<br>
* From === Intel 8272 FDC === NEC uPD765 (or just D765) is exactly the same chip as the 8272. NEC and Intel cross-licensed a bunch of IP back in the day. [https://hackadayforum.comvcfed.org/2012index.php?threads/08/13/taking8272-afdc-lookto-at8-decappeddrive-icsconnections.45816/#commentpost-734991 a comment in the hackaday website557651 Source]: "NEC uPD765 Floppy Disk Controller: Internally this is a microcoded part with a primative controller of NEC’s own design. Testing microcode embedded in a part can be troublesome. The uPD765 had a few extra gates associated with 8272/µPD765 was the DMA Request and DMA Ack pins. Presenting result of a certain illegal combination here places the part into a “test” mode cross-licensing deal between NEC and allows the sequencer microcode to be output on the normal Data pinsIntel. Both were essentially NEC designs.The sequencer microcode is responsible for high level commands such as Read Track, Recalibrate, Format Track, or Write Dataextent of licensing peripheral chips from Intel was pretty broad. There is a similar test mode for the nano[https://classiccmp.org/mailman3/hyperkitty/list/cctalk@classiccmp.org/thread/MMWRWPGKWRVOLMUBIFQTZSCRRMF3YOXF/ Source] [https://scarybeastsecurity.blogspot.com/2020/11/reverse-code array which serializes data at the floppy disk headengineering-forgotten-1970s.html The decapped photos of Intel 8271, NEC D765 and Intel 8272 chips] prove that NEC D765 and Intel 8272 chips are identical."
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