The complaints are certainly about $qio. Some folks even have been trying to use io$_diagnose to read data. Since backup can't write these records (and I can't believe VBACKUP would), it's got to be a $qio issue only. We can certainly limit the large I/O to tape by leaving dkdriver's ucb$l_maxbcnt at 64k, bumping mkdriver's. Won't work for all ports though. Initial assessment: PKCdriver: no way. The chip as I hear can't do more. PKJdriver: Limited somewhat arbitrarily. The claim is that the 64k limit keeps scatter / gather lists from overflow. The scatter gather lists are sgl$k_length, defined in A1742ADEF.MAR as 1048. This may be ok to increase if it matters. I would claim it does not. PKQdriver: Limited somewhat arbitrarily. If PKQ_MAXBCNT and PKQ_NUM_RSPID were boosted from 64k and 255, and maybe a couple other structures were lengthened (I believe some 4K buffers exist but don't see them right off) and some of the MAX_*_ENTRIES params were boosted, it has a good chance of working. PKSdriver (and PKTdriver): Limited arbitrarily. Again, boost PKS_MAXBCNT and NUM_QUEUE_BUFFERS and several other related parameters and it too has a good chance of "just working". PKZdriver: Can't tell what side effects would occur by boosting size. PKEdriver: Can't tell what side effects would occur It may be someone else will have better insight into PKZ, PKE, but I'd suggest that the simplest course would be to do the minor edits to PKS and PKQ, build them, and just try it, bashing the mk ucb by hand if necessary. If they work, they could be left that way (presuming they still are ok for disk, which would continue to be limited by maxbcnt to 64k) and left in as latent support. We could even get some few customers to try them out as patched drivers, gaining some assurance things are OK. The reason I am worried about it is mainly the threat that Boeing might abandon VMS for NT if this can't be solved. (Heard that yesterday second hand...Sue S may know more, or Tom G.) It need not be advertised, but just "be there" so if someone tries this, voila!, it'll work if their port is pks/pkq (or maybe just one). If the quick edits don't work, then it'll need to be considered more slowly and carefully. Glenn