dmt@mtunb.ATT.COM (Dave Tutelman) (07/16/88)
In article <10657@iuvax.cs.indiana.edu> bkliewer@iuvax.UUCP (Bradley Dyck Kliewer) writes: > >Since there seems to be a lot of discussion on the topic of twisted >wires on the controller cables, you might as well know what the twist >does -- it swaps the drive ID lines from between the two connectors. >This is done so that all drives are set to the same ID (who knows why, >I think it's pretty silly myself ... >.... Isn't it wonderful how manufacturer's make little >changes here and there to prevent you from buying other vendor's parts :-)? Having been bitten by this myself when I made my first PC from bareboards (back before this was common knowledge), I think I understand why IBM did it this way. Assuming you meant IBM by your last comment (if you meant Tandy, forgive me), their motive is just the opposite from the one you ascribe. IBM assumed that people might open up their boxes and replace the drives. Unfortunately, every vendor's drive has the strapping option for drive number a little different, and the drives are seldom seen with the documentation that tells how to jumper it. So they set up the PC so that every vendor could ship the drive jumpered for the "standard" drive number, and it would work as either 1 or 2, depending on where it was placed. Works fine, as long as the techie replacing the drive isn't competent enough to try to strap the drive number; in that case, it fails. Assuming IBM expected that the average user (or worse, the average computer salesperson) would be doing the swap, they made a very clever design choice. +---------------------------------------------------------------+ | Dave Tutelman | | Physical - AT&T - Lincroft, NJ | | Logical - ...ihnp4!mtuxo!mtunb!dmt | | Audible - (201) 576 2442 | +---------------------------------------------------------------+