CompuServe Messages

Karl: To change the RESELECTION setting, go in to HDTOOLBOX, highlight the drive on the GVP controller, choose CHANGE DRIVE TYPE, choose DEFINE NEW DRIVE TYPE, and then make sure that SUPPORTS RESELELECTION? is not checked. I'm not real knowledgeable in this stuff so I can't get technical… Joanne Dow left a really good message about RESELECTION… here it is: . #: 27494 S8/System Software . 30-Aug-92 19:27:57 . Sb: #27473-Reselection . Fm: Joanne Dow 71162,3257 . To: Ed Cruse 73307,1465 Reselection is a SCSI process that can make a collection of multiple drives on a single controller work faster as an aggregate. On a SCSI drive you have a lot of smarts. In general there are so many smarts that the drive can intelligently estimate how long it will take to be ready to transfer the data required for the current transaction. If reselection is enabled it can then tell the controller (initiator in SCSIspeak) that "Gee, Boss, this is gonna take me awhile. Disconnect me from the bus and I'll wake you up next time the bus is free and I am ready to process the command." On SCSI controllers that properly handle this reselection process the initiator and target (the drive) return the bus to the "Buss Free" state. The initiator can then scan its "list" if pending commands for a command destined for a different device on that same SCSIbus. If there is one it is free to initiate that command so that you can potentially have several commands all overlapping their processing. When you have multiple drives this can lead to a major speed up in overall processing because otherwise "dead time" is "recycled" into useful purposes. (But in general EACH access will take place slower even if there are no intervening commands because there are more transactions taking place on the SCSI bus.) The upshot of all this is that if you have only one drive run with reselection disabled. (In general do this with Syquests in any case on the A3000. There is "an unfortunate interaction"…) If you have many <continued>