Pertec Tape Drive Interface Musings
Mark J. Blair
nf6x at nf6x.net
Wed Jun 10 11:12:40 CDT 2015
> On Jun 10, 2015, at 08:46, Al Kossow <aek at bitsavers.org> wrote:
> On 6/10/15 8:15 AM, Mark J. Blair wrote:
>> And that is precisely why I'm thinking of an ad-hoc interface rather than just plugging a SCSI drive into a UNIX box.
> It also has the advantage that you can return the CRC/checksum and partially read blocks. Most SCSI tape drives don't
> return the data if the read doesn't succeed.
I particularly like the idea of being able to extract questionable data and CRC/checksum.
Ok, now three more questions come to mind:
1) Is it ever acceptable to mix densities on a single tape? I'm not sure that my Kennedy drive will even allow that, but I don't know if that is universal.
2) What's the scoop on a final record overlapping the EOT marker? Or even a new record starting after the EOT marker? I seem to recall reading about some applications that stuck data after the EOT, such as backup volume information.
3) Did anybody ever go over to the dark side and implement copy protection on magtapes, say, by deliberately including a record with bad CRC that a normal driver+drive would not support writing? Or was that evil limited to the floppy disk world?
Mark J. Blair, NF6X <nf6x at nf6x.net>
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