David Empson wrote:
mdj <mdj.mdj@gmail.com> wrote:Michael J. Mahon wrote:IIRC, the 5.25" drives must be at the end of the daisy-chain, so the last smartport device must synthesize drive 1 and 2 select lines for the downstream devices, and must also pass on (or regenerate) all the standard 5.25" drive signals.That sounds reasonable, yes.I expect that there is an signal line that a drive supplies to the interface that says whether it is a smartport device or not, and the interface responds accordingly, even through intermediate smartport devices.Hmm, I'm not sure how, since the //c Smartport, Liron card and 5.25" controller card are essentially identical, and contain signalling that's only relevant to 5.25" drives.Technically, yes. The IWM and Disk ][ controller provide the same set of signals to the drive connectors, which are sufficient to control 5.25" drives.
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All of the above explains why the drives have to be in a certain order: "Dumb" 3.5" drives need to be first, so they can sense the 3.5DISK signal (not passed on by other drives). SmartPort drives need to be next, since 5.25" drives would be confused by the SmartPort signals. 5.25" drives need to be last, so the other drives can avoid passing signals through when the other drives are being accessed.
This can also be stated as sorting the drives from newest interface to oldest interface, since the older drives cannot route signals introduced in later drives. -michael New, faster SUDOKU v2.0 solver for Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it's seriously underused."