The SCO device drivers have critical timing issues that in some instances require near perfect SCSI bus impedance and termination, and specific firmware releases in host adapters, hard drives, and tape drives to achieve reliable operation. SCO OpenServer 5 in particular is much more timing critical than previous releases. Hence some people say "this hardware worked fine until I upgraded to OpenServer 5, and now it locks up".

Make an archive copy of the file /etc/conf/pack.d/Sdsk/space.c

Edit /etc/conf/pack.d/Sdsk/space.c

Look for the following lines:

int     Sdsk_no_sg = 0;
int     Sdsk_no_tag = 0;
int     Sdsk_set_RCD = 0;           (OpenServer 5 Only)

Change the 0 in each line to a 1.

Save the file, re-link the kernel, and re-boot.

These three lines control Scatter/Gather Enable, Tagged Queuing, and target read cache respectively. Disabling them will slow the system slightly while increasing stability.

If your system remains stable after a week or so of activity you may try enabling these features one-by-one until you fail. Then you'll know for sure which advanced feature causes instability on your system.