Putting a hard drive spindle motor's control signals under an oscilloscope was instructive, even if I don't yet understand everything that's going on. Perhaps I could find some documentation to demystify the magic? I looked for hints on the hard drive control circuit board, which told us this 80GB drive dated from 2002 via "WDC (C) 2002" printed in the lower-left corner.

Motor control wires led to this chip, which has a ST Microelectronics logo. Unfortunately, putting these visible identifiers "L6278 17E H99SF0335" into ST.com site search came up empty. Either my search skills are pathetic, ST website database doesn't go back that far, or this chip is something ST made exclusively for Western Digital under a proprietary contract. What's certain is that I'm not going to learn more about this particular brushless motor controller. Oh well, I'll continue my sightseeing tour.

Next chip over has a Marvell logo. And just like the ST chip, searching for "88C5540-LFE G472261.2 0339 B2S" came up empty.

Infineon TLE4417 is not listed on their own web site, but other sites (mostly trying to sell me some chips) say it is a voltage regulator.

If true, it makes sense to have voltage regulation close to the main controller: a WDC WD70C22.

A controller needs some working memory, which is where this Samsung K4S161622E-TC60 DRAM chip comes in.

I didn't learn very much on this pass, but as I learn more about electronics, I hope future examinations will be more instructive and less of a just-for-fun sightseeing tour like this one. That is yet to be seen, in the meantime I retread familiar ground to take apart this hard drive's mechanical components.

[UPDATE: Sprite took a stab at hard drive controller hacking some time back. Lack of datasheet documentation was a deal-breaking barrier for me, but not for the experienced hardware hacker.]