Home Table Of Contents Support Pages Feedback & Contact Apple Computer, Inc. Mirror Sites Huh? |
By Mark Campbell
Blind transfers refer to the way data is transferred to the hard drive by the driver software. In drive formatting software that supports turning this option on or off, a different version of the driver is written to the driver partition. Apple's Hard drive utility Apple HD SC Setup does not allow you to turn on or turn off blind transfers.
Blind TransfersWhen using blind transfers, SCSI Manager (part of the system software) assumes the data can be written to, or read from the drive as fast as SCSI Manager can read it. If a slow drive is used, there is the potential for data corruption due to timing problems. If the drive cannot write the data fast enough, data is lost because of an overflow of the data buffers. If the drive cannot supply data fast enough during a read, SCSI Manager reads erroneous information from the controller because the data has not arrived yet. By using Blind transfers, the computer can significantly improve the speed of SCSI throughput.
Polled TransfersIf blind transfers are not enabled, polled transfers are used. Polled transfers are used with slow SCSI devices and/or older Macintosh computers. Older, in this case, means the Macintosh SE and Macintosh Plus. In polled transfer mode, the SCSI Manager polls the SCSI controller to see if there is data to be read before reading, or that the last chunk of data was written before sending the next chunk. This is the safest method for doing reads and writes.
Apple HD SC SetupApple HD SC Setup determines whether or not to install the driver which uses blind transfers based on the computer the drive is attached to when it is formatted. Apple HD SC Setup only turns off blind transfers on drives formatted while connected to the Macintosh SE or Macintosh Plus. Since Apple HD SC Setup doesn't support turning on or off blind transfers, you need to purchase drive formatting software that supports this option if your third-party software or hardware manual recommends changing the transfer mode your Macintosh computer currently uses.
 [Previous] [Top] [Next] |
||||
"The Information Alley", in all formats, is copyright Apple Computer, Inc.
All Rights Reserved.
Sometimes you may read in some third-party manuals that you should either turn on, or turn off blind transfers. The question most people have is what are blind transfers, and how do I turn them off or on?