8mm tape on IBM RS/6000

[Ed Kubaitis]

An 8mm tape drive on an RS/6000 running AIX 3.1 appears to take ~30 seconds
doing *something* when opened at load-point. The documentation I have
describes a "retension on open" option, but this delay is encountered even
when a device name for "no retension on open" is used. Further, this option
seems to refer to QIC tapes, not 8mm, anyway. 

Does anybody know what's causing this delay? Is it hardware or software, and
is there a way to prevent it?

2 other questions about 8mm: 

What are "extended file marks" and the pros & cons of using them?

Is there something in 8mm recording comparable to the ARA/AGC "burst" written
at beginning of tape in 1/2" 6250 GCR recording? That is, does one compromise 
data reliability on 8mm tapes by appending data to an existing tape on a 
different drive?

Would appreciate either answers or pointers to people or documents with 
answers. Thanks in advance!

-----------
Ed Kubaitis (ejk at uxh.cso.uiuc.edu)
Computing Services Office
University of Illinois, Urbana