FT//ex and AIC-7770 SCSI Driver Support

The SCO UNIX SCSI driver when first installed with the integral AIC-7770 dual port SCSI system on the FT//ex enables tagged command queues by default. A number of drives do not support this feature and therefore cannot be used until the operating system driver is set to ignore this feature. To set the SCSI driver to disable tagged command queues edit the file /etc/conf/pack.d/Sdsk/space.c and change the line

int Sdsk_no_tag = 0;
to
int Sdsk_no_tag = 1;

and then rebuild the kernel. It is possible to install a machine with drives which do not support tagged command queues but under load random disk or SCSI bus errors are likely to occur until the above modification is implemented.

Please remember that only the following list of drives is currently fully supported and warranted in the FT//ex range. These drives have gone through extensive testing with the main operating systems which has not taken place with other drives. These drives support tagged command queues and no alteration is required to the SCSI driver if only these hard disks are installed in the machine.

Please Note:

This issue of tagged command queues will not occur under MS-DOS or NetWare as these operating environments do not have drivers which support tagged command queues. Windows NT uses tagged command queues by default but this feature can be disabled.

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