re quadra scsi problems attention mac quadra owners many storage industry experts have concluded that mac quadras suffer from timing irregularities deviating from the standard scsi specification this results in silent corruption of data when used with some devices including ultra modern devices although i will not name the devices since it is not their fault an example would be a sony inch mo without the special mac compatible firmware installed one solution sometimes is to disable blind writes to the best of my knowledge there aren t any problems with quadras and blind transfers trouble with blind transfers usually means the programmer screwed up the tibs or didn t test their driver with the device in question well designed tibs poll or loop at every point where delays of sec occur this usually occurs at the first byte of each block of a transfer but some devices can hiccup in the middle of blocks if this happens in the middle of a blind transfer there is the possibility of losing or gaining a byte depending on which direction the tranfer was going in anycase the scsi manager will eventually return a phase error at the end of the transaction because it is out of sync actual data loss would only occur if the driver didn t pay attention to the errors coming back note that this effect is not caused by anything actually on the scsi bus but rather by the transfer loops inside the scsi manager the problem occurs when the processor bus errors trying to access the scsi chip when the next byte hasn t been clocked yet also note that the bus error is dealt with by a bus error handler and doesn t crash the machine clinton bauder apple computer
